Manual roll Flutter Engine from a5f7d5d75ff2 to 8f9e608d39ab (31 revisions)

Manual roll requested by zra@google.com

https://github.com/flutter/engine/compare/a5f7d5d75ff2...8f9e608d39ab

2023-06-09 zanderso@users.noreply.github.com Revert Dart to 3.1.0-180.0.dev (flutter/engine#42688)
2023-06-09 mk12360@gmail.com [fuchsia] Bump the target API level to 12, and pass it to fidlc (flutter/engine#42667)
2023-06-09 bdero@google.com [Impeller] Add tests for foreground blends with mask blurs (flutter/engine#42687)
2023-06-09 godofredoc@google.com Document the use of realm in archives. (flutter/engine#42682)
2023-06-09 skia-flutter-autoroll@skia.org Roll ANGLE from 76b0e7f38b44 to d8339e78db54 (1 revision) (flutter/engine#42684)
2023-06-08 godofredoc@google.com Prevent double upload of benchmarks. (flutter/engine#42683)
2023-06-08 skia-flutter-autoroll@skia.org Roll ANGLE from 5215293366f0 to 76b0e7f38b44 (2 revisions) (flutter/engine#42680)
2023-06-08 godofredoc@google.com Remove all the uses of master branch in the .ci.yaml file. (flutter/engine#42679)
2023-06-08 godofredoc@google.com Replace benchmarks with its v2 version. (flutter/engine#42677)
2023-06-08 bdero@google.com [Impeller] Reorder blend filter checks to avoid unnecessary destination snapshot (flutter/engine#42678)
2023-06-08 bdero@google.com [Impeller] Specify blend mode on blend filter commands (flutter/engine#42676)
2023-06-08 skia-flutter-autoroll@skia.org Roll ANGLE from c49674d1565c to 5215293366f0 (1 revision) (flutter/engine#42673)
2023-06-08 rmolivares@renzo-olivares.dev [Linux] composing delta fixes (flutter/engine#42648)
2023-06-08 jinhe.zjh@alibaba-inc.com Fix: invalid time-point comparison between each from different clock source (flutter/engine#42409)
2023-06-08 zanderso@users.noreply.github.com Fix license hash (flutter/engine#42675)
2023-06-08 zanderso@users.noreply.github.com Revert Dart to 3.1.0-184.0.dev (flutter/engine#42671)
2023-06-08 skia-flutter-autoroll@skia.org Roll ANGLE from b5d261ac5c5b to c49674d1565c (2 revisions) (flutter/engine#42670)
2023-06-08 skia-flutter-autoroll@skia.org Roll Dart SDK from b7fe6e0c274c to 3a9145a57432 (1 revision) (flutter/engine#42668)
2023-06-08 jonahwilliams@google.com [Impeller] sort all vertex inputs by location. (flutter/engine#42664)
2023-06-08 skia-flutter-autoroll@skia.org Roll ANGLE from 05e087658b10 to b5d261ac5c5b (1 revision) (flutter/engine#42662)
2023-06-08 zanderso@users.noreply.github.com Revert "[Impeller] Added a switch to turn on vulkan" (flutter/engine#42660)
2023-06-08 skia-flutter-autoroll@skia.org Roll ANGLE from 15a29438b099 to 05e087658b10 (6 revisions) (flutter/engine#42659)
2023-06-08 skia-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from aMTaMP0DdKdJnxSbc... to lPCv1NshK-tvjtLgC... (flutter/engine#42658)
2023-06-08 skia-flutter-autoroll@skia.org Roll Fuchsia Mac SDK from DL1QQ5eZRVNARqLx-... to ukXXOXtI7uRIukzF5... (flutter/engine#42655)
2023-06-08 skia-flutter-autoroll@skia.org Roll Dart SDK from f0ae96d202ca to b7fe6e0c274c (1 revision) (flutter/engine#42657)
2023-06-08 skia-flutter-autoroll@skia.org Roll Dart SDK from 9e633e463902 to f0ae96d202ca (1 revision) (flutter/engine#42651)
2023-06-08 godofredoc@google.com Benchmarks configurations for engine v2. (flutter/engine#42622)
2023-06-08 skia-flutter-autoroll@skia.org Roll Skia from 1a3adf848e61 to 8fdbbca7d35d (1 revision) (flutter/engine#42645)
2023-06-08 skia-flutter-autoroll@skia.org Roll Dart SDK from bbce07ad3944 to 9e633e463902 (3 revisions) (flutter/engine#42646)
2023-06-07 aam@google.com Roll dart to 3.1.0-180.0.dev (flutter/engine#42638)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from 156542f8bf13 to 1a3adf848e61 (1 revision) (flutter/engine#42644)

Also rolling transitive DEPS:
  fuchsia/sdk/core/linux-amd64 from aMTaMP0DdKdJ to lPCv1NshK-tv
  fuchsia/sdk/core/mac-amd64 from DL1QQ5eZRVNA to ukXXOXtI7uRI

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC jacksongardner@google.com,rmistry@google.com,zra@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

...

Reverts flutter/flutter#127391

I'm back from OOO so change the test owners back.

Bumps integration tests (that are not run manually only) using `compileSdkVersion` 31 to 33.

This is a refactor to make `MouseTracker` use the same callback for both kinds of device update. Instead of using two different callbacks for the two device updating methods, `MouseTracker` now receives a hit testing callback at construction, which is the same hit testing method as the one used for other gestures.

This PR not only makes the code cleaner, but also removes the single view assumption from `MouseTracker`, whose code no longer refers to `RendererBinding.renderView`. In the future, we only need to modify `hitTest` (which we will have to do to support gestures for multi-view anyway) to make mouse tracker support multi-view.

Fixes https://github.com/flutter/flutter/issues/44118

Fixes: https://github.com/flutter/flutter/issues/127228

## Description

This adds `AppLifecycleListener`, a class for listening to changes in the application lifecycle, and responding to requests to exit the application.

It depends on changes in the Engine that add new lifecycle states: https://github.com/flutter/engine/pull/42418

Here's a diagram for the lifecycle states. I'll add a similar diagram to the documentation for these classes.

![Application Lifecycle Diagram](https://github.com/flutter/flutter/assets/8867023/f6937002-cb93-4ab9-a221-25de2c45cf0e)

## Related Issues
 - https://github.com/flutter/flutter/issues/30735

## Tests
- Added tests for new lifecycle value, as well as for the `AppLifecycleListener` itself.

This widget implements the ability to place slivers one after another in
a single ScrollView in a way that all child slivers are drawn within the
bounds of the group itself (i.e. SliverPersistentHeaders aren't drawn
outside of the scroll extent provided by all of the child slivers). The
design document for SliverMainAxisGroup can be found
[here](https://docs.google.com/document/d/1e2bdLSYV_Dq2h8aHpF8mda67aOmZocPiMyjCcTTZhTg/edit?resourcekey=0-Xj2X2XA3CAFae22Sv3hAiA).

Fixes https://github.com/flutter/flutter/issues/33137.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

---------
Co-authored-by: Kate Lovett <katelovett@google.com>

I'm getting a few false positives in https://github.com/flutter/flutter/pull/128522/checks from the `num.clamp` checker since I introduced a class with a `clamp` method.

Fixes https://github.com/flutter/flutter/issues/128430

This attempts to reland https://github.com/flutter/flutter/pull/126848

This was reverted because it made some unexpected changes to our perf measurements. After landing https://github.com/flutter/flutter/pull/127900, we have much less noise in our benchmarks, so I'd like to reland this and see if there is still a significant measurement difference.

*The order of calling Navigator.pop and PopupMenuItem.onTap has been changed so before calling PopupMenuItem onTap method, PopupMenuBotton onSelect method is going to be called.*

*Solves #127443*

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*

This updates dartdoc to 6.3.0.  Release notes are available, here:

https://github.com/dart-lang/dartdoc/releases/tag/v6.3.0

Most important for Flutter are the reduction in the size of generated HTML files (dart-lang/dartdoc#3384) and a new dartdoc directive to hide constant implementations from indicated classes (dart-lang/dartdoc#3398), which fixes the longstanding issue (dart-lang/dartdoc#2657).

I've also added the api documentation zip to `.gitignore` and the `{@hideConstantImplementations}` dartdoc directive to the motivating example.  A screenshot:

![Screenshot 2023-06-07 at 9 54 58 AM](https://github.com/flutter/flutter/assets/14116827/1ad9c1f0-b224-462f-a8e3-706d9858f0d8)

I assert that this change to icons.dart should be test-exempt as existing tests cover whether or not dartdoc directives are recognized or are leaking into HTML, and the impact of adding the directive was tested in dart-lang/dartdoc#3398.

Fixes https://github.com/flutter/flutter/issues/108187

Many parts of the floating cursor selection feature is pretty tricky. Some took me a while to figure out. So I added some comments to explain a bit for future readers.

*List which issues are fixed by this PR. You must list at least one issue.*

https://github.com/flutter/flutter/issues/30476

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*

This method lived on RenderObjectElement because traditionally, it would be the only one that had to deal with multiple children. The method itself has nothing RenderObjectElement specific, though, and can also be used by any other Element subclass that has multiple children. We are introducing one of those in the near future to handle multiple top-level views.

This is a straight up copy&paste move, no changes have been applied to the code itself.

Follow-up to https://github.com/flutter/flutter/pull/128287.

https://github.com/flutter/packages/compare/a84b2c2ac344...e13b8c43386a

2023-06-08 stuartmorgan@google.com [tool] Only run unit tests in Chrome for inline web (flutter/packages#4153)
2023-06-08 jason-simmons@users.noreply.github.com [in_app_purchase] Make the _FeatureCard constructor const in the Android example app (flutter/packages#4162)
2023-06-08 stuartmorgan@google.com [shared_preferences] Fix initialization race (flutter/packages#4159)
2023-06-07 47866232+chunhtai@users.noreply.github.com [go_router] Refactors imperative APIs and browser history (flutter/packages#4134)
2023-06-07 stuartmorgan@google.com [various] Add `http` 1.0 compatibility (flutter/packages#4147)
2023-06-07 32538273+ValentinVignal@users.noreply.github.com [go_router_builder] Accept required parameters not in path (flutter/packages#4039)
2023-06-07 engine-flutter-autoroll@skia.org Roll Flutter from 0b741535 to 8a5c22e2 (46 revisions) (flutter/packages#4160)
2023-06-07 scheglov@google.com [pigeon] Require analyzer 5.13.0, prepare for NamedType refactoring. (flutter/packages#4127)
2023-06-07 engine-flutter-autoroll@skia.org Roll Flutter (stable) from f92f44110e87 to 682aa387cfe4 (1 revision) (flutter/packages#4157)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages-flutter-autoroll
Please CC flutter-ecosystem@google.com,rmistry@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

https://github.com/flutter/flutter/issues/128440

The current version of the action has a bug where the sync-labels default value is not read correctly. Explicitly setting to see if that stops the removals.

Most of the tests are using Chrome 96.2, which is quite old. Update to Chrome 114.

Reverts flutter/flutter#128471

It looks like one of the tests modified by this PR is still failing: https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/11385/overview

This PR adds uses of the `--target-os` command line argument when
building kernel sources for precompiled applications for supported
target operating systems. The Dart CFE then:

* treats `Platform.operatingSystem` as if it were defined as the
constant string provided as an argument to the flag,
* treats `Platform.pathSeparator` as the appropriate separator for that
operating system,
* attempts to constant evaluate the initializer for any field annotated
with the `vm:platform-const` pragma, and
* attempts to constant evaluate all calls to a method annotated with the
`vm:platform-const` pragma.

The `vm:platform-const` pragma can appear in either library or user
code. If the attempt to constant evaluate the field initializer or
method call fails, then an error is thrown at kernel compilation time.

Addresses #14233.

The tests in
`packages/flutter_tools/test/general.shard/build_system/targets/common_test.dart`
have been adjusted properly to account for the new passed command line
arguments.

https://github.com/flutter/engine/compare/1089ce6874cf...a5f7d5d75ff2

2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from c5a8c4547f59 to 156542f8bf13 (4 revisions) (flutter/engine#42641)
2023-06-07 jason-simmons@users.noreply.github.com Roll HarfBuzz to 7.3.0 (flutter/engine#42629)
2023-06-07 zhangzhijian.123@bytedance.com [Impeller] Corrected the 'texture_coords' computation in 'Geometry::GetPositionUVBuffer' (flutter/engine#42619)
2023-06-07 aam@google.com Roll dart to 3.1.0-171.0.dev (flutter/engine#42636)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from 773765ca1dd2 to c5a8c4547f59 (4 revisions) (flutter/engine#42633)
2023-06-07 godofredoc@google.com Add global test docs. (flutter/engine#42531)
2023-06-07 skia-flutter-autoroll@skia.org Roll Fuchsia Mac SDK from ojwVlxZWrbsG4WGSE... to DL1QQ5eZRVNARqLx-... (flutter/engine#42632)
2023-06-07 skia-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from sEHtHM1iFt79roP-x... to aMTaMP0DdKdJnxSbc... (flutter/engine#42631)
2023-06-07 chillers@google.com [labeler] Fix to run on flutter/engine (flutter/engine#42634)
2023-06-07 leroux_bruno@yahoo.fr [iOS] Fix TextInputAction.continueAction sends wrong action to framework (flutter/engine#42615)
2023-06-07 jonahwilliams@google.com [Impeller] fix missing assignment of embedder render target. (flutter/engine#42630)

Also rolling transitive DEPS:
  fuchsia/sdk/core/linux-amd64 from sEHtHM1iFt79 to aMTaMP0DdKdJ
  fuchsia/sdk/core/mac-amd64 from ojwVlxZWrbsG to DL1QQ5eZRVNA

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC jacksongardner@google.com,rmistry@google.com,zra@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
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Documentation for the AutoRoller is here:
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## Description

Changes the context menu example for `MenuAnchor` so that it uses right-click, or (on macOS and iOS only) ctrl-left-click, for the context menu. Also disables the browser context menu on web platforms.

## Tests
 - Updated test to reflect new triggers.

fixes https://github.com/flutter/flutter/issues/120408

Added two gradle tasks, one for grabing the application id, one for grabbing app link domains.

Added a new vmservices to call these two gradle tasks and return the result.

The expected work flow is that the devtool will first call a vmservices to grab all avaliable build variants. It will then choose one of the build variant and call this new services to get application id and app link domains.

https://github.com/flutter/engine/compare/4f4486b00be2...1089ce6874cf

2023-06-07 jonahwilliams@google.com [Impeller] Add buffer to texture
blit for Vulkan. (flutter/engine#41706)
2023-06-07 chris@bracken.jp [macOS] Add platformview creation parameter
support (flutter/engine#42607)
2023-06-07 30870216+gaaclarke@users.noreply.github.com [Impeller] Added
a switch to turn on vulkan (flutter/engine#42585)
2023-06-07 skia-flutter-autoroll@skia.org Roll ANGLE from f8220fa3a729
to 15a29438b099 (1 revision) (flutter/engine#42627)
2023-06-07 jacksongardner@google.com Bump Chrome version to 114 for
testing (flutter/engine#42623)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from d607cbb0db78 to
773765ca1dd2 (7 revisions) (flutter/engine#42624)
2023-06-07 jpnurmi@gmail.com [Linux][a11y] implement
AtkText::get_text/string_at_offset() (flutter/engine#38144)
2023-06-07 skia-flutter-autoroll@skia.org Roll ANGLE from 176989ad00cc
to f8220fa3a729 (1 revision) (flutter/engine#42621)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from ee90e9ae2e62 to
d607cbb0db78 (1 revision) (flutter/engine#42618)
2023-06-07 skia-flutter-autoroll@skia.org Roll ANGLE from 1ad4ae4d63bf
to 176989ad00cc (1 revision) (flutter/engine#42617)
2023-06-07 dkwingsmt@users.noreply.github.com Revert "[Android] Return
keyboard pressed state" (flutter/engine#42616)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from bde894438f29 to
ee90e9ae2e62 (1 revision) (flutter/engine#42614)
2023-06-07 skia-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from
lpbkSRJBMkPs0FM7_... to sEHtHM1iFt79roP-x... (flutter/engine#42613)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from cd3e1665dcd1 to
bde894438f29 (1 revision) (flutter/engine#42612)
2023-06-07 skia-flutter-autoroll@skia.org Roll ANGLE from 16841d6256da
to 1ad4ae4d63bf (1 revision) (flutter/engine#42611)
2023-06-07 bdero@google.com [Impeller] Reland 2: Add Impeller Metal
support in the embedder API (#42411) (flutter/engine#42597)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from a01f49f539ab to
cd3e1665dcd1 (1 revision) (flutter/engine#42610)
2023-06-07 skia-flutter-autoroll@skia.org Roll Fuchsia Mac SDK from
atrYtfHWi2cmV9B_C... to ojwVlxZWrbsG4WGSE... (flutter/engine#42609)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from 521b8c4bb011 to
a01f49f539ab (4 revisions) (flutter/engine#42608)
2023-06-07 skia-flutter-autoroll@skia.org Roll Skia from cef18d10b363 to
521b8c4bb011 (1 revision) (flutter/engine#42605)

Also rolling transitive DEPS:
  fuchsia/sdk/core/linux-amd64 from lpbkSRJBMkPs to sEHtHM1iFt79
  fuchsia/sdk/core/mac-amd64 from atrYtfHWi2cm to ojwVlxZWrbsG

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC jacksongardner@google.com,rmistry@google.com,zra@google.com on
the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter:
https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
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Documentation for the AutoRoller is here:
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## Description

Fix two typos where 'wether' was used instead of 'whether'.

## Tests

Documentation only.

Roll to engine to 4f4486b00be28183b482bbb74bbed25f4db153fe  pick up dart to 3.1.0-169.0.dev.
Changes since last roll
```
4f4486b00b Roll dart to 3.1.0-169.0.dev (#42602)
```

Manual roll since rolling to dart 3.1.0-169.0.dev requires patching to expression evaluation in flutter tools

https://github.com/flutter/packages/compare/da72219048fc...a84b2c2ac344

2023-06-06 stuartmorgan@google.com [ci] Exclude maps unit tests on Windows (flutter/packages#4152)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages-flutter-autoroll
Please CC flutter-ecosystem@google.com,rmistry@google.com on the revert to ensure that a human
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To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

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Just now I see some good news: https://www.reddit.com/r/FlutterDev/comments/13vo5a2/the_most_important_flutter_310_feature_that/ (ignore the title though...). It was a performance problem in the old days, so it was great that the problem disappears. However, it seems that the doc is not updated yet, so everyone reading MediaQuery page will still use the old way. Thus I create this super-tiny PR :)

Reverts flutter/flutter#128095

We have a tree closure related to the `widget_inspector_test.dart`. I'd
like to see if reverting this resolves the issue.

Fixes: https://github.com/flutter/flutter/issues/127215

Closes https://github.com/flutter/flutter/issues/106416.

This PR adds a new `flutter config` setting named `jdk-dir`. When set, the tool will use the JDK found at this location for all Java-dependent tool operations such as building Android apps via gradle and running Android SDK tools.

https://github.com/flutter/engine/compare/6f9df0f988c1...59d5444cf06c

2023-06-07 jason-simmons@users.noreply.github.com Convert pixel formats for animated PNG frames using the source blend mode (flutter/engine#42581)
2023-06-06 skia-flutter-autoroll@skia.org Roll ANGLE from e21ecd1b59f7 to 16841d6256da (24 revisions) (flutter/engine#42601)
2023-06-06 skia-flutter-autoroll@skia.org Roll Skia from 4065e92bf577 to cef18d10b363 (18 revisions) (flutter/engine#42600)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC jacksongardner@google.com,rmistry@google.com,zra@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
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https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Fixes https://github.com/flutter/flutter/issues/127090.

https://github.com/flutter/flutter/pull/122505 did a few things to speed up the first asset load that a flutter app performs. One of those things was to not include the main asset in its own list of variants in the asset manifest. The idea was that we know that the main asset always exists, so including it in its list of variants is a waste of storage space and loading time (even if the cost was tiny).

However, the assumption that the main asset always exists is wrong. From [Declaring resolution-aware image assets](https://docs.flutter.dev/ui/assets-and-images#resolution-aware), which predates https://github.com/flutter/flutter/pull/122505:

> Each entry in the asset section of the pubspec.yaml should correspond to a real file, with the exception of the main asset entry. If the main asset entry doesn’t correspond to a real file, then the asset with the lowest resolution is used as the fallback for devices with device pixel ratios below that resolution. The entry should still be included in the pubspec.yaml manifest, however.

For example, it's valid to declare `assets/image.png` as an asset even if only `assets/3x/image.png` exists on disk.

This fix restores older behavior of including a main asset as a variant of itself in the manifest if it exists.

This fix also includes a non-user-visible behavior change:
* `"dpr"` is no longer a required field in the asset manifest's underlying structure. For the main asset entry, we do not include `"dpr"`. It makes less sense for the tool to decide what the default target dpr for an image should be. This should be left to the framework.

This PR updates the docs for Transform.Scale constructor by clearing up some ambiguity regarding how the scaling factor is affected by the omission of a value given you provide scaleX and scaleY as arguments as opposed to just scale

addresses bug [126822](https://github.com/flutter/flutter/issues/126822)

- [X ] I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
- [X ] I read the [Tree Hygiene] wiki page, which explains my responsibilities.
- [ X] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
- [X ] I signed the [CLA].
- [X ] I listed at least one issue that this PR fixes in the description above.
- [ X] I updated/added relevant documentation (doc comments with `///`).
- [ X] I added new tests to check the change I am making, or this PR is [test-exempt].
- [X ] All existing and new tests are passing.

... found when looking at leak tracker today.

By the way, shall we add some kind of automatic link linter, which goes through all links and see whether they are alive?