Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

* Move the handling of delegating AppDelegate callback out of FlutterAppDelegate.

Also moves the plugin registry to FlutterViewController. So each view-controller will handle its
own plugins.

This is intended to simplify including one or more Flutter views in an existing iOS app and giving
more precise control of plugin registration.

Fixes: https://github.com/flutter/flutter/issues/16539

* formatting

* Update license golden file

* update docs for getBounds

* Add computeMetrics suggestion

* better explanation

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

With this change if flutter tools provides isolateId parameter, then VM will run the handler on that isolate. If no isolateId is provided, VM will continue running handlers as if they were registered wit Dart_RegisterRootServiceRequestCallback.

This goes towards fixing https://github.com/flutter/flutter/issues/17434

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

iOS does not allow usage of OpenGL ES APIs when the app has been moved to the
background.  With this change, the shell will wait until pending IO thread tasks
complete and the Skia unref queue is drained before proceeding with shutdown.

See https://github.com/flutter/flutter/issues/17511

Update engine for removal of Dart_ReadKernelBinary and refactored build targets.

Auto-roller completed checks. Merging.

This reverts commit 755dbeef.

Update engine for removal of Dart_ReadKernelBinary and refactored build targets.

The Fuchsia bots seem to reference this target to figure out the root_out_directory https://fuchsia.googlesource.com/build/+/master/dart/dart_test.gni#67. Note that the presence of the flutter_tester binary location itself is not depended on. Instead, the target is used to infer the directory containing the flutter_tester after a build.

Patching the //build repository in Fuchsia would mean making the tree red till a //topaz patch lands. To avoid doing this, we add back the missing reference.

This allows applications to start a Flutter engine instance during app startup
and keep it running throughout the app process' lifetime.

FlutterActivity subclasses can override createFlutterNativeView to provide a
preinitialized FlutterNativeView instance and override retainFlutterNativeView
to signal that the FlutterNativeView should be kept alive when the activity
is destroyed.

Auto-roller completed checks. Merging.

s/`[red]`/_correct color_.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.

Auto-roller completed checks. Merging.