Updating base turns out to be more complicated than I thought.

This reverts commit daa822aa.
This reverts commit c38428c7.
This reverts commit 4b73a8a0.

Update base, gn, and their clients.

These files are generated to different paths now.

The upstream mojo.git no longer contains this code.

iOS: Discard the depth and stencil attachments of the framebuffer before presenting the color renderbuffer. (#2737)

- [x] Wire up synchronous script reloading in the library tag handler.
- [x] Allow glfw sky_shell to start from dart source as well as bundle.

This patch moves the remainder of painting and compositing into their
new home (and updates their style to match Google C++ Style).

This should make almost every Canvas call significantly faster.

These parts don't depend on engine anymore. Also reformat them to match Google
C++ style.

This patch moves the geometry classes.

Because we're not using array buffers to marshall the vertex data for
drawVertices and drawAtlas, we need to process the paint argument first so that
we don't call Dart_GetField after creating a view into an array buffer.

* Implement Canvas.drawPoints

This enables drawing polygons faster than using Paths.

Fixes https://github.com/flutter/flutter/issues/92

* Implement more Path functions

Path.fillType
Path.addPolygon
Path.addPath
Path.extendWithPath
Path.transform

Fixes https://github.com/flutter/flutter/issues/252

The only remaining calls to Dart_GetField are for Paint, which will be
handled in a later patch.

This patch removes code in //skia that we don't use.

This patch disentangles dart:jni from //sky/engine and moves it into
//flutter/lib/jni. Eventually dart:ui will move into a peer directory.

This patch removes a number of the classes that were generating
Dart_GetField calls, particularly related to drawAtlas and drawVertices.
The functions that used these classes now use primatives instead, which
is more efficient.

We don't use this code anymore.

Now that tonic doesn't depend on anything in //sky/engine anymore, we
can move the code to a location where its dependencies are clearer.

This patch removes spurious dependences on other parts of the engine.

This patch paves the way to untangling a large amount of code from the engine.

This is the only readback from the canvas API. Having a write-only interface
will unlock future optimizations. This function has no clients.

Fixes #4254

update Dart to get https://github.com/dart-lang/sdk/commit/6b6d363900373a56caa971b5610b3a0050ed55f6 (#2734)

According to hackbod on Stack Overflow, we're supposed to block in the
surfaceCreated callback until we've actually drawn into the surface:

http://stackoverflow.com/questions/8772862/surfaceview-flashes-black-on-load/8888108#8888108

1) Add ability to specify a system UI overlay style, to
   provide a hook into the style of the status bar icons on iOS.

2) Migrate the Activity service's task description API to the
   system chrome platform service. The old API will be removed
   once the Flutter repo is updated to use the new API after an
   engine roll.

flutter/flutter#3544

This patch makes the sdk_xcode_harness work the same way as
hello_services. The goal is to eventually make these the same, but this
is just a first step.

Revert "Codesign pub package vended service dylibs after copying them to the application bundle. (#2727)" (#2730)

This reverts commit 85e2ce27.

This patch breaks the flutter build bots.