Move initialization of device scale factor

R=sky@chromium.org
http://crbug.com/300831

Review URL: https://codereview.chromium.org/25096003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226029 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226029