Now they all flow through some common routines.

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 plugin is implemented internally by the engine to integrate with the asset
system.

Add plunbing for Host-to-Dart platform messages

We'll use the plumbing in this direction for things like key events.

After this patch, platform messages now take the same path through the system
that semantics data does (on Android). Support on iOS will be in another patch.

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 only ever had one UIDelegate. We might as well have people use the Engine
interface directly.

This patch moves the rest of the clients to use the new PointerData
transport.

This patch prepares us to switch sending semantics information over mojom to
using dart:ui directly. Currently the recorded information is dropped on the
floor, but that will improve in future patches.

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.

Depending on the type of bundle path specified, initialize either the zip or directory asset bundle. (#2933)

Regression introduced in https://github.com/flutter/engine/commit/cee7fef7

Also, rename SkyViewClient to RuntimeDelegate. These names are more
sensible.

This patch also cleans up the RuntimeDelegate a bit, for example by
removing support for flushing real-time events, which aren't used.

Now lib/ui depends on sky/engine rather than the reverse.

This pulled a refactoring of how we keep track of the primary threads.

All that's left is two task runners, which should be statics somewhere.

There are now three ways to start Dart applications:

1) From a precompiled snapshot
2) From a snapshot
3) From source

When loading from source, we no longer use the complex data pipe /
dependency catcher mechanism. Instead, we just load the source
synchronously from the file system. This is appropriate because running
from source is used only during development and not during production.

The previous design was built assuming we would want to run from source
over the network, which meant we needed to be able to load source
asynchronously over a high latency channel.

We now just call stat directly to test whether a file exists.

This patch hides the base::SingleThreadedTaskRunner, which pulls a big
switchover to ftl::WeakPtr and std::function.

Add an association between FlutterViews and Dart Isolates to the PlatformView service protocol support (#2886)

This patch centralizes the asset bundle processing in //flutter/assets and
removes the //base dependency from the code.

* Update to mojo ba13534f2b2af27a1d73e176f7406dbab25f8e14

* Fix build for updated mojo

* Fix android build. Undo some of the mojo roll.

* Fix iOS build.

Also, remove the hacks that integrate Skia ref counting with WTF. Now we
just use sk_sp everywhere for managing Skia ref counts.

This patch removes almost all //base dependency of //flow. The only dependency
left is on tracing.

* Update to mojo 7d579155cc597aa3befcbfad66eef54bda06b57c

* Update to new API

Previously we would hold the layer tree until the we returned from Dart. Now we
send the layer tree to the rasterizer thread immediately.

Fixes #212

The layout protocol in Mozart changed. Now we need to pipe a scene version
through the system to the compositor.

SkyShell now supports --packages instead of --package-root.

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.