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.

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

* Update to mojo ba13534f2b2af27a1d73e176f7406dbab25f8e14

* Fix build for updated mojo

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

* Fix iOS build.

This removes most (all?) of our dependency on base::RefCountedThreadSafe.

Also pick up some needed fixes to FTL and Tonic

* Roll Dart to pickup new BoringSSL

* Roll further to pick up build file fixes

Fixes https://github.com/flutter/flutter/issues/4957

We will eventually remove our version of tonic and use this one instead.

This patch starts the process of porting Flutter to run on Fuchsia by
adding FTL to DEPS. We will eventually replace //base with //lib/ftl.

- [x] Fixes devfs opening too many files.
- [x] Build fixes related to Fuschia support

Remove dependencies on ui, third_party/mesa and mojo/convertors. Provide simple alternatives. (#2783)

- Pick up fix for 64-bit AOT/caching-JIT snapshots.

- clustered serialization (dart-lang/sdk@524fbc1e0f9d61ff5da69bbed2b35745528de945)
 - background finalization (flutter/flutter#3804)

https://github.com/flutter/flutter/issues/4560