Webkit: squashed unsupported reverts

Summary:
Reverts of the following due to lacking necessary
HTML5 video frame capture support in external/webkit
Directly conflicts with D600

Revert "webkit: Manage video playing state properly when browser goes to background"

This reverts commit 4106f9a668d64946e780fdeb965d7e6163d9ddec.

Revert "webkit: Fix for unable to play youtube in browser"

This reverts commit ef6d6e3c6e7e5b183c2b5a435561343f96cd740e.

Revert "webkit: Support video frame capture for HTML5 canvas use cases"

This reverts commit 24b5e6dc76ccc1ff464e4b3a794a52d43120224e.

Test Plan: Play youtube in stock browser

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D601