Tweaks near Material, BoxDecoration, implicit animations.

Some more asserts and toString info.
Reorder some code to group lerp-related functions.

clarify that start defaults to checked

Handle degenerate transforms better

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

Remove clamp() in favour of double.clamp()

fixes to flutter analyze for the latest dev sdk

don't listen for chromium messages to the adb log

Fixes #1213.

Also, update callers of deprecated methods.

Floating Action Button transitions

When the scaffold's floating action button (FAB) is replaced the old FAB shrinks to zero and then the new one grows to its full size. When a FAB is shown, its child spins into place.

This is all intended to be a good approximation of the "Lateral Screens" section of the material design spec.

The fab.dart example is included as stop gap until the gallery and other demos have been updated.

starter app now has a button that does something

Fix time picker

We were painting the contents of the RRect clip at the wrong offset. This patch
makes RRect match Rect and Path clips.

Fixes #1194

Teach analyze how to print out the total time spent

Makes it more obvious that flutter analyze takes a long time.

@Hixie

Fixes #961

Provide a safe time to update a WidgetToRenderBoxAdapter

If you change the RenderObject tree between frames, you'll assert if
you subsequently hit test. So e.g. if you get two button presses back
to back, and you mutate the tree synchronously in response to the
first one, the second will assert.

This adds an onBuild callback to WidgetToRenderBoxAdapter to make it
easier to do the updates at the right time, i.e., during widget build.
It'll be called whenever you rebuild the WidgetToRenderBoxAdapter
itself, so all you have to do to use it is call setState() on whoever
is building the WidgetToRenderBoxAdapter.

Stop passing bogus bounds to SceneBuilder

Fixed the RaisedButton shadow issue

We no longer need to pass bounds to SceneBuilder. Instead, the
compositor computes these bounds itself from the RTrees in the
SkPictures.

ShaderMask needs to play nicely with compositing

The onHighlightChanged callback was being given "true" every time
instead of the actual value.

This patch adds ShaderLayer and makes ShaderMask use it.

Fixes #1155

Transition callers from 'concat' to 'transform'

Add reference to "mojo:media_service" in sound.dart

Related: https://github.com/domokit/mojo/issues/614

Flutter can play sounds using this package. However, when Mojo Shell is running Flutter, it lacks the necessary media service.

This patch creates a hook to the mojo binary `media_service.mojo`. If Mojo Shell is built with this media service, then it will be able to play sounds when running Flutter.

RenderPerformanceOverlay needs alwaysNeedsCompositing

The performance overlay is always drawn using the compositor. We should tell
the rest of the system that it's going to make a composited layer.

Fixes #1177

Use a named argument for Widget children