* Reland "Roll engine to version b148e628ec86b3a9a0382e0bcfae73f0390a8232 (#20427)"
This is a re-land with downgraded `package:flutter_gallery_assets`
version.
* Downgrade package:flutter_gallery_assets to 0.1.4
* Change engine.version to 81baff97c29bb08cbf8453a3f9042c5813f84ad3 (which contains an additional fix)
* Change engine.version to e3687f70c7ece72000b32ee1b3c02755ba5361ac (since mac tarballs are corrupted on earlier commit)
Rewrote CupertinoAlertDialog to look nearly identical to an alert dialog in iOS. This includes considerations for blur, translucent white background color, button sizing, gap dividers between buttons, and text scaling layout behavior. (#18381)
With this change you can now create "wrapping" text fields that do not show the new line button:
```dart
new TextField(
maxLines: null,
keyboardType: TextInputType.text,
);
```
In the event that no Dart VM's exist or are connectable, will instead
await for a new Dart VM to show up. Will no longer return null when
calling `getMainIsolatesByPattern`, instead returning either a list of
isolates or timing out.
Reason for revert: The package:flutter_gallery_assets has removed some images which are required for the examples/flutter_gallery, so the gallery build is failing (only discovered after landing, since gallery doesn't seem to get built during github PR presubmit checks)
This CL
* rolls `engine.version` to flutter/engine@b148e628 (which includes dart sdk 2.1.0-dev)
* rolls `goldens.version` to flutter/goldens@6c45fafdf (which includes updates due to skia changes in engine)
* changes `platform.dill` to `platform_strong.dill` in various places due to flutter/engine@a84b210b
* adds explicit `environment: sdk: ">=2.0.0-dev.68 < 3.0.0"` constraints to `pubspec.yaml` and `pubspec.yaml.tmpl` files (since pub defaults to `<2.0.0` if omitted)
* upgrades to newer versions of various 3rd party packages (to ensure transitive dependencies have `<3.0.0` sdk constraint)
* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test
In certain cases, the test would fail before creating the (lazily created) compiler object, and then we'd
try to call shutdown() on null in those cases.
Fixes#18610
This adds the animation links for illustrations of the Transition widgets, as well as adding a cross-references to the other transition widgets in the "See also" for each of their docs.
Resizing an AndroidView happens asynchronously (as it requires thread
hopping from the ui thread to the platform thread).
While waiting for the resize to complete the framework does exactly when
the embedded view has been resized. This leads to pretty bad jank as the
framework might paint the embedded view with a wrong size.
We're working around this by freezing the texture frame while resizing
until we are sure that the next frame has the new size. This is how it
looks with the workaround:
This is how it looks before and after the workaround:
Before (janky) | After (less janky)
:--------|---------:
 | 
This depends on flutter/engine#5938. Additionaly right now the engine completes
the resize call immediately, a following PR will change it to complete
after a frame with the new size is ready.
This PR adds 2 features to RenderAndroidView and AndroidView:
1. Hit testing behavior
Adds a `PlatformViewHitTestBehavior` which is similar to
`HitTestBehavior` without the `deferToChild` option (as platform views
don't have child render objects) and with a `transparent` option which
prevents it from forwarding any events to the Android view.
2. MotionEvent recomposing logic
FlutterView and the framework `converter.dart` are working together to
transform each Android MotionEvent object into one or more
`PointerEvent` objects.
This PR adds the reverse logic (in _MotionEventDispatcher which is used
by RenderAndroidView) which turns a stream of PointerEvent objects into
MotionEvent objects.
The correctness of the recomposing logic is tested in an integration
test which will land in a separate PR (the unit test PR is pretty big,
trying to keep as many bite-size PRs for reviewer's convenience)
