Breaking change: removed facilities for JSON and string messaging from FlutterView/FlutterViewController, leaving only binary messaging there. All other use of flutter communication now goes through FlutterMessageChannel and FlutterMethodChannels. Retained use of String and JSON codecs for now.

Companion flutter PR: flutter/flutter#8837

See https://github.com/flutter/flutter/issues/7561

Flutter channels now also supported on iOS. Use FlutterMessageChannel or FlutterMethodChannel with binary/string/json/standard codecs.

New concepts: FlutterMessageChannel (basic message send/receive superseding existing FlutterView methods), FlutterMethodChannel (method invocation and event streams), pluggable codecs for messages and method calls: unencoded binary, string, json, and 'standard' flutter binary encoding.

The PlatformView superclass constructor was posting a task to the UI thread
that adds the view to the shell's global list.  This could result in UI thread
operations seeing PlatformView instances that are not fully constructed and do
not yet have an engine.

This was happening in https://github.com/flutter/flutter/issues/7735

Adapt to refactoring of snapshot APIs in the Dart VM.

The GPUSurfaceGL holds references to Skia objects that may own GL objects.
If the GL objects are destructed on the GPU thread after the EGL context has been
dropped, then the GL delete calls will not take effect.

This was causing exceptions on Jellybean

Fixes https://github.com/flutter/flutter/issues/6586

Fixes https://github.com/flutter/flutter/issues/7226

Add a getter for flutterView in FlutterActivity. This allows fullscreen flutter apps to extend FlutterActivity and do custom stuff with the flutter view. (#3324)

Detach the EGL surface from the GPU thread and then destroy it during the FlutterView surfaceDestroyed callback (#3316)

Fixes https://github.com/flutter/flutter/issues/7147

Fixes https://github.com/flutter/flutter/issues/7234

FlutterView's host message processing methods are invoked from native code,
and the JNI wrappers will abort the process if the Java side has an uncaught
exception.

Initialize the InputConnection with the text plugin's most recent state (either incoming or outgoing) (#3283)

Fixes https://github.com/flutter/flutter/issues/7033

We push a bit up the tree during preroll to learn whether there system
composited layers below each layer. During update scene, we squash down
to paint tasks, which we execute after publishing the new scene.

I updated the C++ and Dart sides but forgot to update the Java side.

Fixes https://github.com/flutter/flutter/issues/6891

These are implemented on macOS and Fuchsia.

(JSONObject.getString() will return the string "null" for a JSON null value)

Fixes https://github.com/flutter/flutter/issues/6643

Update DartServiceIsolate/FlutterView because VMServiceIO_NotifyServerState
now provides a URI for the observatory

Initialize AndroidSurfaceGL and its associated resource context before ANativeWindow acquisition. (#3193)

* Initialize AndroidSurfaceGL and its associated resource context before ANativeWindow acquisition.

This allows us to create the IO thread context way earlier and service load requests on the same. Before this patch, early lifecycle loads would use the default Skia texture loader instead of the Async texture loader we provide.

Fixes https://github.com/flutter/flutter/issues/6581

* Don't destroy surface_gl_ PlatformViewAndroid::ReleaseSurface.

After this patch, we no longer link with Mojo. We still use some gn definitions
from //mojo to create Dart packages.

We had a typo in our decoding logic.

Fixes https://github.com/flutter/flutter/issues/6564

We no longer use mojom to transport messages. We still use the Mojo EDK
to spin the event loop, however.