Add support for transformations.

This change adds partial support for the following transforms:
- scale()
- translate()
- rotate()
- setMatrix()
- getMatrix()

The transform is stored in a snapshot and saved/restored as needed.
The transform is currently not applied to the clip rect and is not
mapped to the vertex shader.

Change-Id: Id48993453311200804149917d0c126a4d0471226