Add policies to allow events named Dwm* in the gpu sandbox. 

These events are created/opened by dwmapi.dll and are needed for the XP presentation path to work in the restricted gpu
sandbox. The other change is to run this in the restricted sandbox.

BUG=299047
R=cpu,jbauman

Review URL: https://codereview.chromium.org/24911002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226074 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226074