Instead of a PNG, the Flutter gallery widget is now drawn in code.

There's now a FlutterLogoDecoration class that paints the flutter logo
anywhere you can use a Decoration (e.g. AnimatedContainer).

There's now a FlutterLogo class that honors the IconTheme.

The About dialog box API now takes a Widget for the applicationIcon,
instead of an ImageProvider. It uses IconTheme to make the icon the
right size instead of using an Image widget.

Add padding, duration, and curve properties to the DrawerHeader.
Make the child of a DrawerHeader optional.

Clean up UserAccuntsDrawerHeader a bit.

Add some useful properties and methods to EdgeInsets.

Add some debug logic to RenderDecoratedBox to catch unpaired
save/restore calls when possible.

Make GestureDetector fill its parent if it has no children. Fixes
https://github.com/flutter/flutter/issues/5380