Fix a lock re-entry bug in GpuDataManager::UpdateGpuInfo.

The issue is that the registered callbacks could request GPUInfo, so they could re-enter the lock.  Therefore, we should release the lock before we run through callbacks.

BUG=84805
TEST=the issue in 84805 is gone.
Review URL: http://codereview.chromium.org/7054063

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@87898 0039d316-1c4b-4281-b951-d872f2087c98