Fix the dismissible demo in the gallery (make it actuall update when you pick something from its menu; give it a better affordance for resetting once you've dismissed everything).

Improve some docs.

Fix various flinging bugs with dismissible. Add tests for those cases.

Add a feature to flutter_test to support a drag-then-fling gesture (used by the flinging tests).

* feat: add optional headers params to network image

* fix: addressed comments

* feat: add test

* style: format code

* Add missing onDragCompleted to LongPressDraggable

* Add test for LongPressDraggable onDragStarted and onDragCompleted

Changed the ExpansionTile widget to have an optional value to
initialize the widget as collapsed or expanded.

The widget will be collapsed by default.

Use of this file was eliminated in e7657b94.

This fixes the popup menu code to do a better job of expanding
smoothly regardless of which side of the screen it's on. It still
results in a bidirection growth when positioned at the bottom of the
screen, so maybe we'll need to animate menus differently, but that's
a problem for another patch.

Also, improve some docs and provide RelativeRect.toSize which I needed
at one point while building this patch (though it didn't survive all
the way to the end).

* clear timeline events prior to starting a new action

* trailing commas

Fixes #12877 by reverting #9472

* AnimationController reset() method

Just a simple convenience method to fix #13039

* Added `reset()` test

* More test expectations

Per feedback.

* Removed test print

* Improved documentation of reset()

* Add controller.reverse to test

* Show Android tombstone during native crash

* Fix tombstone lines being missed on newer Android versions

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.