Cherry-pick: Create WindowAndroid to make PowerSave work.

BUG:11553674

This is the cherry-pick of 2 chromium CLs.

https://codereview.chromium.org/29303004/
Original description:
Make WindowAndroid constructor takes context as param.

https://codereview.chromium.org/65683003/
Orignal description:
Create WindowAndroid in WebView.

Change-Id: I0969f46ca9dba40e8eef843dceda66e6a4c9b036
7 files changed