This makes sure that we don't decode frames when we don't need to run
the animation.

For example, prior to this CL: an animated image in a page that is not
currently at the top of the page stack (it is covered by another page),
will keep the the image stream listener, and thus frames will still be
decoded.

* Add caching detail in doc

* review

This reverts commit 1abd8a12.

This allows `flutter run` to work on hosts that are IPv6-only.

In 77af1e5e, dart:vmservice_sky was
renamed to dart:vmservice_io.

Picks up Dart SDK roll to 3ee0a4284203ebc6991c78054583a7c02dc8faf9

* Add support for NDK discovery and add --prefer-shared-library option

We would like to be able to use native tools (e.g. simpleperf, gdb) with
precompiled flutter apps.  The native tools work much better with *.so
files instead of the custom formats the Dart VM uses by default.

The reason for using blobs / instruction snapshots is that we do not
want to force flutter users to install the Android NDK.

This CL adds a `--prefer-shared-library` flag to e.g. `flutter build
apk` which will use the NDK compiler (if available) to turn the
precompiled app assembly file to an `*.so` file.  If the NDK compiler is
not available it will default to the default behavior.

* Rebase, add test for NDK detection, augment flutter.gradle with @Input for flag

* Use InMemoryFileSystem for test

* Remove unused import

* Address some analyzer warnings

1. We want to measure wall-clock duration for the benchmarks, as opposed
   to thread duration (e.g., waiting on a mutex should accrue time) and
   'dur' is the metric to use for that.

2. On Darwin-based systems (macOS and iOS) 'tdur' is the result of a
   mach syscall lookup to thread_info. This call returns unreliable data
   on iOS. Chromium, for example, disables thread time support entirely
   for iOS.

I get this error when piping an `echo` string to the stdin of
the flutter tool.

https://github.com/dart-lang/sdk/issues/29083

Adds a test that verifies that the microtask queue is flushed between
engine event loop iterations.

Related issue: https://github.com/flutter/flutter/issues/9998

I got tired of drive-by spelling fixes, so I figured I'd just take care of them all at once.

This only corrects errors in the dartdocs, not regular comments, and I skipped any sample code in the dartdocs. It doesn't touch any identifiers in the dartdocs either. No code changes, just comments.

This fixes DropdownButtons to align their popups correctly in RTL as well.

Also while I was there I fixed the issue with text scale factor in the gallery.

Previously, we were mapping certain named platforms
(e.g. `android-stable`) to their corresponding version.
this had two problems:

1. The version could become out of date. For instance, we had
   mapped `android-stable` to version 24, but the stable version
   is now 27.
2. The list of possible named versions wasn't comprehensive.
   Some Android SDKs just list the platform as `stable`, or
   `experimental`, etc.

This change updates the platform version detection to use
the `build.prop` file that exists in the platform directory
(only for cases where the version number is not encoded into
the directory name).

This is the first engine role with libwebp, so we expect an increase in
flutter app sizes.
I'll be monitoring the app size benchmarks after this lands.

Previously, ExpansionPanel would do weird things if interacted with
when it was already animating. This is fixed and there's now a test.

Also:

 * Minor fixes to make the gallery work in RTL, not that there's
   any way to see that without hard-coding the framework to RTL.
   But at least I'll be less annoyed when doing that.

 * Some trivial code and documentation cleanup.

* custom hashCode/== in Element to speed up inheritFromWidgetOfExactType

* explain why 24 bits

This makes ListTile expand vertically when text is scaled, or really when whatever is placed inside it is larger than the available space.

In order for UnconstrainedBox to be useful here, I needed for it to only unconstrain the child Row in one dimension, so I added a "constrainedAxis" parameter to the UnconstrainedBox.

Also, changed one enum test to use a switch instead.

I modified the ListTile test to be more representative of the intention of the spec: we were testing with text in the leading and trailing sections, and the design wants icons there. Because there was leading text, and the dense mode only changes the font size on the text lines, the leading text was propping up the minimum size of the tile, making so that the test wasn't really testing any changes in dense mode.