Fix fullscreen media control position issue when switching orientation

Currently we force page scale factor to 1.0 in fullscreen mode (whether it is
a video or not). The assumption was broken when switching orientation. Adding
extra check in screen resize code to make sure the constraint is enforced.

R=aelias,qinmin
BUG=376408

Review URL: https://codereview.chromium.org/308513002

git-svn-id: svn://svn.chromium.org/blink/trunk@175018 bbb929c8-8fbe-4397-9dbb-9b2b20218538