Round the size of shared memory regions up to 64K. This allows

      native client modules to map these regions.  With this fix,
Pepper audio works on all three platforms.

Review URL: http://codereview.chromium.org/1242006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@42621 0039d316-1c4b-4281-b951-d872f2087c98