Don't crash when destoying transfer buffer that isn't mapped.

It's possible GetTransferBuffer was never called, or that it failed due to a GPU process crash, so don't crash when the transfer buffer isn't in the cache.


BUG=https://code.google.com/p/chrome-os-partner/issues/detail?id=14476


Review URL: https://chromiumcodereview.appspot.com/11270036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@164174 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed