* Fine-tune iOS's scroll start feel

* remove negations in doc

* Our own dart-side gesture arena also contributes to the 'jerk'. Make sure that snap is accounted as well.

* Added more code comments from review.

Fixes #14590.

This moves --vm_snapshot_data and --isolate_snapshot_data argument
hardcoding from GenSnapshot (a minimal wrapper around gen_snapshot
invocations) to Snapshotter.buildScriptSnapshot(). These arguments are
present in both AOT and script snapshots, but differ semantically: for
script snapshots they're inputs from the host engine artifacts
directory, for AOT snapshots they're outputs to the build directory.

This is a PR giving some love to the abandoned PR #16263 by @harrisonturton

I've added a test, and formatted it to be readable.

Currently the CircleAvatar does not set a fit property on the DecorationImage it uses to paint images. This causes non-square images to not fully cover the circle, which looks pretty bad. This PR sets it to BoxFix.cover.

Fixes #13478.

We're seeing occasional test timeouts trying to call `FlutterDriver.connect()`.
Unfortunately, when the test is timed out at the test runner level, you don't
get a meaningful test failure or stack trace of where the timeout occurrred.
Your test harness also doesn't get to clean up, which can include things like
saving the device logs to see what was going on in the device.

Thus, this change adds timeouts in the places where we've most
commonly observed hangs during tests.

This roll includes the following commits.

* flutter/engine@637e921d6: Use the raster cache when rendering screenshots as bitmaps (#5050)
* flutter/engine@a23fa923c: Look for an assets path specification in the Info.plist. (#5049)

* update engine version, ignore scopesRoute and namesRoute flags until framework support is added

This contains the following commits:

flutter/engine@3cc8d82 Fix more Linux unittest targets.
flutter/engine@b6ba69b libtxt: add boxes representing empty lines in GetRectsForRange
flutter/engine@388f019 Enable downscale of very large images when uploading on IO thread
flutter/engine@22e1381 Allow runtime unit-test to perform dynamic symbol resolution for Dart snapshots.
flutter/engine@59d1366 Don’t build the host shell on target builds.
flutter/engine@7a6b779 Remove the weak pointer factory from the service isolate's DartIsolate object
flutter/engine@d4729ab Update the embedder GN target to use a source set instead of a complete static library.
flutter/engine@8973c73 Implement Scene::toImage for creating a raster image representation of a scene.
flutter/engine@572c584 Configure kernel paths in the embedder if the asset directory contains the kernel assets
flutter/engine@8ed932c Roll src/third_party/skia/ 1cd6098d5..1ccaa6e05 (20 commits)
flutter/engine@a0804f3 Simplify weak pointer factories and allow vending weak pointers on multiple threads.

Adding some tests for onTapDown and onTapCancel for the InkWell, as suggested in post-submission comments by @Hixie in #16190.

Also, added those to the diagnostic output.

* Run tests in dart2 mode.

* Fix type check

* Drop --checked, leave --preview-dart-2

* Remove debugging leftovers.

Support summary-details tree view.

This contains the following commits:

flutter/engine@5822b6e Clear the canvas when attempting to render to the surface.
flutter/engine@d8eb659 Make the rasterizer own the compositor context.
flutter/engine@387945c Correct ninja command instruction
flutter/engine@00911b2 Don't send platform messages to isolates that are not running.
flutter/engine@5c857ee Set the start timestamp in the contructor of the first shell.

This roll includes the following engine commits:

* flutter/engine@0c09bf03: In the service protocol, if no view is specified to flush tasks on, pick the first one. (#5028)
* flutter/engine@ecaefd7a: Roll src/third_party/skia/ 276886160..1cd6098d5 (50 commits) (#5026)
* flutter/engine@e6545573: Enable 'Speak Screen' and 'Switch Control' for iOS (#5016)
* flutter/engine@3393c179: Fix Android platform channels (#5025)
* flutter/engine@1bc0e1bb: On windows, refer to Dart snapshot directly executable. (#5024)
* flutter/engine@cf6ca32d: Revert "Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79" (#5023)
* flutter/engine@4b45a53e: Only make ERROR and FATAL log levels visible by default. (#5022)
* flutter/engine@98f6c2d5: Fix shell launcher test (dart2 compliant and stop polling) (#5009)
* flutter/engine@75851f08: Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79 (#5020)
* flutter/engine@9495a52d: On iOS, try to use ES3, then fall back to ES2. (#5006)
* flutter/engine@d6d4eec2: Fix broken Linux build (#5019)
* flutter/engine@d15dc76e: Fix broken Chromebot build (#5018)
* flutter/engine@c17a6290: Breadcrumbs to the wiki (#5017)
* flutter/engine@4eaf2c2f: Return raw (unencoded) bytes in Image.toByteData() (#5008)
* flutter/engine@d812a617: Roll src/third_party/skia/ e669bdfad..276886160 (9 commits) (#5014)
* flutter/engine@62aeab72: Call SkSurface::flush instead of getting a backend handle in vulkan_swapchain. (#5012)
* flutter/engine@f4ebb180: Roll src/third_party/skia/ 3462eb034..e669bdfad (54 commits) (#5007)
* flutter/engine@0b7d6be9: Re-land "do not pause rendering when android view loses focus" (#5004)
* flutter/engine@91dee598: If the rasterizer has a valid surface context, use that to create a snapshotting render target. (#4979)
* flutter/engine@570231b7: Specify the packages file path when running engine dart tests. (#5005)
* flutter/engine@0b9cef5a: Minor update to README (#5003)
* flutter/engine@c386418f: Promote line height in text style created from paragraph style (#4995)
* flutter/engine@4e0fbb6f: If the test specifies a .dill file, dont make the engine interpret is as source. (#5002)
* flutter/engine@58e84c8b: Re-land "Support multiple shells in a single process. (#4932)" (#4998)
* flutter/engine@37e5df05: Remove only use of SkPaint::kGenA8FromLCD (#4994)
* flutter/engine@b7358b33: libtxt: cache font families that are remapped to the default font family (#4990)
* flutter/engine@a530035b: libtxt: fix leaks in Skia object reference counting (#4988)
* flutter/engine@0c74fc93: [fuchsia] Fix use-after-free (#4987)
* flutter/engine@b6d2dde9: [fuchsia] Fix build (#4986)
* flutter/engine@1dd12649: [async] Adapt to libasync API changes. (#4980)

Adding missing docs to the forceRebuild function in the widget inspector.

This will catch the case where tests hang -- and it will
force them to fail so that we see the output from the test.

Finalizers handle the restoration of state. In order to restore
the state correctly, they shouyld be run in LIFO order.

Fixes #16657

* Roll engine to d6d4eec24c38bb06a9b1aef4e70c321d447ba762

Contains the following engine commits:

flutter/engine@1bc0e1b On windows, refer to Dart snapshot directly executable.
flutter/engine@cf6ca32 Revert "Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79"
flutter/engine@4b45a53 Only make ERROR and FATAL log levels visible by default.
flutter/engine@98f6c2d Fix shell launcher test (dart2 compliant and stop polling)
flutter/engine@75851f0 Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79
flutter/engine@9495a52 On iOS, try to use ES3, then fall back to ES2.
flutter/engine@d6d4eec Fix broken Linux build
flutter/engine@d15dc76 Fix broken Chromebot build
flutter/engine@c17a629 Breadcrumbs to the wiki
flutter/engine@4eaf2c2 Return raw (unencoded) bytes in Image.toByteData()
flutter/engine@d812a61 Roll src/third_party/skia/ e669bdfad..276886160 (9 commits)
flutter/engine@62aeab7 Call SkSurface::flush instead of getting a backend handle in vulkan_swapchain.
flutter/engine@f4ebb18 Roll src/third_party/skia/ 3462eb034..e669bdfad (54 commits)
flutter/engine@0b7d6be Re-land "do not pause rendering when android view loses focus"
flutter/engine@91dee59 If the rasterizer has a valid surface context, use that to create a snapshotting render target.
flutter/engine@570231b Specify the packages file path when running engine dart tests.
flutter/engine@0b9cef5 Minor update to README
flutter/engine@c386418 Promote line height in text style created from paragraph style
flutter/engine@4e0fbb6 If the test specifies a .dill file, dont make the engine interpret is as source.
flutter/engine@58e84c8 Re-land "Support multiple shells in a single process.
flutter/engine@37e5df0 Remove only use of SkPaint::kGenA8FromLCD
flutter/engine@b7358b3 libtxt: cache font families that are remapped to the default font family
flutter/engine@a530035 libtxt: fix leaks in Skia object reference counting
flutter/engine@0c74fc9 [fuchsia] Fix use-after-free
flutter/engine@b6d2dde [fuchsia] Fix build
flutter/engine@1dd1264 [async] Adapt to libasync API changes.

* Run test platform finalizers in reverse order to ensure that shell is shutdown before trying to delete any temporary files or directories. This fixes "Access Denied" error on Windows (see #16657).

The engine expects it to always be there.

* add localizations for navigation menu, popup menu, dialog, and alert

Support exposing the InspectorService over the Flutterservice extension protocol as well as the observatory protocol. (#15876)

* Support exposing the InspectorService over the Flutter
service extension protocol as well as the observatory protocol.

We will probably remove most of the observatory protocol support once a
couple versions of the Flutter IntelliJ plugin have shipped that use the
Flutter service extension protocol. The only reason to continue supporting
the observatory protocol is it will allow using the inspector when paused
at a breakpoint.

This reverts commit b0b2c007.

* Turn support for sync-async on in Flutter. With this feature
execution of async functions starts immediately instead of it
being delayed by one microtask tick.

* Address review comments.

* Adjust some stack trace expectations which are slightly different with
--sync-async turned on.

We don't really like the name AnimatedChildSwitcher, and we think that AnimatedSwitcher might be better (since the Child part is redundant). We also considered AnimatedChild, AnimatedTransition and AnimatedReplacement (among others).

Nothing in here besides a rename.

* Don't return null, just rethrow RpcException error when vmservice responds with error.