Fix scrollable tabs, add basic unit test

test harness for stocks app on iOS

Restored overlay_geometry example

Adds teleporting methods for moving sprite kinematic bodies

Animated sprite physics bodies now correctly transfers energy to dynamic bodies

The goal is to follow the guidelines in
https://github.com/flutter/engine/blob/master/sky/specs/style-guide.md#packages

Fixes #1638

Export new InputEvent classes from appropriate places

It's OK to just specify the colors list.

Fixes SpriteBox to work better with native points

Improves sprite physics debug drawing

Arena sweep

Fix warnings seen when running skyanalyzer in strong mode

Teach dumpRenderTree() to draw actual trees.
Make the TextStyle output terser so it doesn't overflow the output.
Make debugDumpApp() say what mode we're in (checked vs release).
Hide lifecycle state from release mode dumps (since it's checked-only state).

Fixes touch handling and refactors sprite physics

We had a typo in our CSS translation.

Implement better synchronization between the state of the input widget and the keyboard IME

Add a ListItem widget

For those times where you want to spin something around a point relative
to the size of your box, but you don't know the size of your box.

Also add an input widget API for the keyboard submit button

Add dart-layer input event abstraction

Adds missing sprite physics shapes