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

Now we just pass the data directly.

Previously, these signals were sent over Mojo. Now we send them through
platform messages.

Instead, just use JNI and Objective-C directly.

This patch removes the use of the host messages mojom and switch all
message routing over to platform messages.

Clients have been migrated to the TextInputPlugin.

This plugin will eventually replace keyboard.mojom.

This will replace raw_keyboard.mojom.

This patch completes the routing for Java-to-Dart platform messages.

This functionality has been replaced by the PlatformPlugin. Also move the
contents of //flutter/services/common to more sensible homes.

To make the default state all zeros.

Fixes https://github.com/flutter/flutter/issues/6236

The PlatformPlugin is the first of the built-in plugins that will replace the
mojom platform services.

TalkBack still isn't fully working, but this patch gets us much closer.

This transport uses the Dart and JNI APIs directly instead of indirecting
through Mojo.

We now use JNI rather than Mojo to transport pointer data from Java to Dart.
Also, fill in a few more of the pointer data fields from information in Java.

* Namespaces have been updated to reflect the move from //flutter/sky/shell to //flutter/shell.
* shell/BUILD.gn file has been split into smaller GN files for each subcomponent of the shell (common, GPU, diagnostic, testing).
* GN dependencies have been rewritten to stop exposing common shell dependencies as public. Duplicates have also been removed.
* GPU subcomponent has been updated make it more suitable for Vulkan integration.
* The GLFW backend has been resurrected.

We need to block in the surfaceChanged callback until we can swap the GL
surface with some content in order to avoid flashing transparent and then
black.

Fixes https://github.com/flutter/flutter/issues/5373

This requires adding a way for platform services (namely SystemChromeImpl) to
listen for activity lifecycle events

Fixes https://github.com/flutter/flutter/issues/4885

It's empty and is easily confused with onPostResume

This will make it simpler to write listeners that can be reused in multiple
applications.

Tools can send a broadcast intent that will cause Flutter processes to
write their names and observatory ports to the log in JSON format.

Partial fix for https://github.com/flutter/flutter/issues/2950

These are now offerred by the Flutter platform services (e.g., SystemChrome,
SystemSound, HapticFeedback).

This include build system changes for selecting Dart's precompiler mode
plus a way to locate and load the precompiled snapshot library from an
Android application

This patch cleans up the public Java interface to the Flutter engine. The code
that we intend to be re-usable is now in the io.flutter.view package. The two
public classes are:

 * FlutterMain, which controls initialization of the system, and
 * FlutterView, which is an Android view that hosts a Flutter app.

We'll need to interate on these interface over time, but at least these names
are more reasonable.

These services are relative to the current view, which means they should come
in through the view services.

This patch cleans up the way we expose Mojo services into Dart. It also adds a
service provider for "view services," which will evetually contain the raw
keyboard service.

Previously this value was the temp directory that we used to store the FLX
bundle. Now it's the URL given to us by MojoShell.

Make the engine private to the Sky package and expose the relevant public methods on PlatformViewAndroid