Made the engine and the view controllers have BinaryMessengers, not be
BinaryMessengers.  This allows us to break retain cycles and makes the
leaking channels we have not less dire.

This reverts commit 2f36285b.

This was crashing the integration test `- (void)testDualFlutterView`.

Created FlutterSurrogateBinaryMessenger to make sure that channels are
holding onto engines and not viewcontrollers.  This doesn't change the
public API but makes clients do what we want them to be doing, using
Engine for FlutterBinaryMessenger.

* Revert "[fuchsia] Fix alignment of Fuchsia/non-Fuchsia tracing (#9289)"

This reverts commit f80ac5f5.

* Revert "Align fuchsia and non-fuchsia tracing (#9199)"

This reverts commit 78265484.

Preserve safe area on Window regardless of insets.

This PR updated the forwarding gesture recognizer to pass the touch events directly to the FlutterViewContoller instead of FlutterView which ensures the touches events are passed to the framework.

Some components in the Flutter engine were derived from the forked blink codebase. While the forked components have either been removed or rewritten, the use of the blink namespace has mostly (and inconsistently) remained. This renames the blink namesapce to flutter for consistency. There are no functional changes in this patch.

* Mark const extern

* fix build

* Break cycle between FlutterViewController and FlutterEngine

According to Apple's [OpenGL ES Programming guide][1], applications
should pause any animations in applicationWillResignActive. Any GL calls
after applicationDidEnterBackground will cause the app to be terminated
immedidately by iOS.

The surfaceUpdated:YES call is moved to the handler for the
applicationDidBecomeActive notification to handle cases where the
application becomes inactive then active again without being
backgrounded (e.g. home button double-tap then return to app directly).

[1]: https://developer.apple.com/library/archive/documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/ImplementingaMultitasking-awareOpenGLESApplication/ImplementingaMultitasking-awareOpenGLESApplication.html#//apple_ref/doc/uid/TP40008793-CH5-SW1

Prepend [NSLocale currentLocale] for first locale on iOS to ensure countryCode exists. Allow language-only locales. (#6995)

* Make sure to not unset a11y flags on reentrant calls to API

* Ignore multiple attemps to set splash screen, print warning

* fix setInitialRoute

This PR breaks PlatformViewsController's construction dependency on FlutterView,
which allows making FlutterEngine its owner instead of
FlutterViewController.

Also renamed the FlutterScreenshotDelegate to FlutterViewEngineDelegate
which is FlutterView's delegate to the engine, and expanded it to
provide a view embedder.

For flow to manipulate the embedded UIViews during the paint traversal
it needs some hook in PaintContext.
This PR introduces a ViewEmbeder interface that is implemented by the
iOS PlatformViewsController and plumbs it into PaintContext.

The ViewEmbedder interface is mainly a place holder at this point, as
this PR is focused on just the plumbing.

* Create FlutterEngine to manage a Shell to support maintaining execution state across instances of FlutterViewControllers
* Refactor PlatformViewIOS to support adding or removing a FlutterViewController dynamically
* Refactor FlutterDartHeadlessCodeRunner to implement FlutterEngine
* Refactor FlutterViewController to accept a FlutterEngine at initialization or to create one for backwards compatibility; any Shell related responsibilities are now passed through to the Engine instance
* Remove FlutterNavigationController (unused)
* Update all public Objective C doc comments to be consistent and formatable
* Add public documentation to all public headers

Adds a FlutterPlatformViewFactory protocol - a simple factory protocol to be implemented by plugins
  that exposes a UIView for embedding in Flutter apps.
* Adds a FlutterPlatformView protocol, which is used to associate a
  dispose callback with a `UIView` created by a FlutterPlatformViewFactory.
* Exposes a registerViewFactory method in FlutterPluginRegistrar.
* Implements the `flutter/platform_views` system channel on iOS, allowing
  Dart code to ask for creation/destruction of UIViews.

* Allow FlutterViewController to specify whether its FlutterView is opaque

* Locale Passing

* Pass full locale list and script and variant codes to framework

* Working Android locale list passing and fallback

* Publish port of observatory over mDNS

Add a `-[FlutterViewController setFlutterViewDidRenderCallback:]`
method on iOS so client applications can be notified when the Flutter
view has rendered.  This can be used for add2app cases to determine
when to take an initial screenshot for comparisons in automated
tests.

The callback is expected to be an Objective-C block (or Swift
closure).  I chose to support only a single callback because it's
much simpler (especially since it does not require a separate method
to unregister the callback), and it's not clear that there are use
cases that would justify additional complexity.  Clients have the
flexibility to make their callback invoke other callbacks anyway.

I alternatively considered adding a `-[FlutterViewController
viewDidRenderFirstFlutterFrame]` method that clients could override
in a subclass, but using an Objective-C block seems more flexible and
less of a burden.

Fixes https://github.com/flutter/flutter/issues/20665

Remove touch mapper and respect the UITouch phase when calculating the pointer data change type. (#6430)

The touch mapper was a relic of a time when the pointer IDs had to be less
than 16. Not respecting the touch phase is getting in the way of clients that
fake their own touches. Turns out the AppDelegate also like to fake touches to
simulate status bar events. Now, except in cases where there is a specific
override in place, the UI touch phase is respected.

* SystemNavigator.pop can pop w/o UINavigationController

* If isolate is already running, return true

* Use shell::Engine::RunStatus as result of Engine::Run