Add various trace events for tracing startup

Add back log statement used by Flutter tools to detect trace capture

@abarth

Update style guide to recommend `flutter analyze`.

Add a counter to trace VSync events from the platform

Allow capturing unified (Dart and base) traces from observatory

* Start capturing via <obs_host>:<obs_port>/flutter_startTracing
* Stop capturing via <obs_host>:<obs_port>/flutter_stopTracing

Only strip executable in release builds on Mac/iOS

Flip y coordinate on FNL as a workaround

Add --flx flag to load FLX files

SkyShell on Mac shows a blank window

When I run SkyShell on Mac from the command line, I get a blank screen unless I
make the change in this patch.

Also, remove the --snapshot flag because using FLX files is the path we're
paving.

Have Travis check the build for Dart errors.

Flutter for Modroid should use vsync

This patch teaches Flutter how to connect to the vsync service on Modroid.
Also, remove our now-redunant copy of vsync.mojom.

Fixes #589

Rev engine.

Fix Rect.isEmpty

...and provide Size.isEmpty and Size.shortestSide for consistency.

Layers don't always have paint bounds.

Remove static data from Java keyboard-related service implementations

Fixes #299

URLConnections hold a strong reference to their delegate. Remove previous hack to hold on to the delegate manually.

Remove previous hack to hold on to the delegate manually.

Don't tie the lifecycle of the NSURLConnection to that of the URLLoader and disable NSURLConnection caching

URLLoader and disable NSURLConnection caching

Add system-level routing

We now respect the "route" field in Intents to load a route other than '/'.
Also, use popRoute rather than events to indicate that the framework has asked
us to go back.

Move all engine generated resources into a single directory in the Xcode project