Get windowless plugins working when accelerated compositing is turned on by copying the buffers using skia instead of OS specific ways that need the platform device.

Also remove the code that kept the background buffer in sync with plugins since it's not necessary anymore. Looks like Flash and Silverlight support this correctly now.
Review URL: https://codereview.chromium.org/11361170

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@167042 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed