Basic implementation of the AndroidOverlay framework.  Requests to
create an overlay will create a do-nothing overlay impl.

Adds the first instance of a Java-only mojo interface to the GPU
interface registry.

BUG=691283
TEST=mojo_android_overlay_unittest

Review-Url: https://codereview.chromium.org/2688193002
Cr-Commit-Position: refs/heads/master@{#457964}