Make checkForSiblingStyleChanges and checkForEmptyStyleChange into methods on Element

We always passed |this| into these functions, they should just be private
methods instead.

Review URL: https://codereview.chromium.org/64113005

git-svn-id: svn://svn.chromium.org/blink/trunk@162136 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Changing can-play-webm layout test for Opus

Opus has been enabled by default in Chromium. Changing the layout
tests so that canPlayType returns probably for opus.

Note: This should not be submitted until
https://codereview.chromium.org/62183002/ lands.

BUG=315606
R=scherkus@chromium.org

Review URL: https://codereview.chromium.org/71653011

git-svn-id: svn://svn.chromium.org/blink/trunk@162137 bbb929c8-8fbe-4397-9dbb-9b2b20218538