Cherry-pick: [WebView] Create PowerSaveBlocker for fullscreen video.

Cherry-picked from chromium:
https://crrev.com/ec9b8860c670221d8bfcfbe628f0597a5b6bd4f6

BUG:17653054

Original description:

[WebView] Create PowerSaveBlocker for fullscreen video.

BUG=417623
Committed: https://crrev.com/ec9b8860c670221d8bfcfbe628f0597a5b6bd4f6
Cr-Commit-Position: refs/heads/master@{#296738}

Change-Id: Ic58ff0fd7684cec4276950887d9a5ea186f2f8f6
4 files changed