We get the icons from the iconfont now.

Also, remove the package:flutter CHANGELOG.md.  This file is outdated and the
git history is a more accurate change log these days.

The mojo_sdk has cleaned up its dependencies, so we no longer need to depend on
package:test from package:flutter.

This patch switches us from using our previous hacking approach to integrating
with package:test to using the new PlatformPlugin interface.

See the comment in the patch for details.

Downloading these packages from cloud storage simplifies our deployment
story because we can upload to cloud storage automatically from the
buildbot.

This patch also switches the responsibility for downloading the engine
artifacts to update_engine.sh. Centralizing this responsibility ensures
that the packages and the binaries are always in sync.

This reverts commit b240cda8.

This reverts commit ab300634.

Third-party libraries can now provide their own mojo services. They do
so by adding a config.yaml file to their pub package which contains
- a list of service names and java classes which handles that service's
  registration.
- a list of pre-built .jar files to statically link with the app's shell
  when building the app.

The dart bindings changed semantics in a non-compatible way.

No you can't hit things inside degenerate transforms. Tranforming from global
coordaintes to degenerate local coordinates gives you Point.origin. Also,
upgrade vector_math to get a better invert constructor.

Fixes #1161
Fixes #1224

Also, update callers of deprecated methods.

Fixed #1009