Always write data to new buffer in SimulateAttrib0

This is to work around linux nvidia driver bug.

TEST=asan
BUG=118970


Review URL: http://codereview.chromium.org/10019003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@131538 0039d316-1c4b-4281-b951-d872f2087c98