content: Use setLoadWithOverviewMode() instead of setInitializeAtMinimumPageScale().

setInitializeAtMinimumPageScale() is marked as deprecated in Blink's WebSettings
API. So we should migrate chromium to setLoadWithOverviewMode(). After this
lands, setInitializeAtMinimumPageScale() will be removed from Blink.

BUG=None
TEST=None
R=jochen@chromium.org,jamesr@chromium.org

Review URL: https://codereview.chromium.org/57143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232734 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232734