Convert 3D Graphics section from devsite to reST.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3634
NOTRY=true
(documentation-only change)

Review URL: https://codereview.chromium.org/24824002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231101 0039d316-1c4b-4281-b951-d872f2087c98
Added unit tests to ensure damage of layers not drawn because of their parent is preserved properly.

BUG=291218

Review URL: https://codereview.chromium.org/41683002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231102 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231101
SVN changes up to revision 231102