Avoid compositing when the surface texture is still empty.

This avoids rendering a white layer in the surface view before the first frames
from blink are available and instead we continue rendering the theme
background in the Android activity until then.

BUG=307113

Review URL: https://codereview.chromium.org/62333022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235984 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235984