Create org.chromium.content_public.common and move two classes there.

ScreenOrientationValues and Referrer are being moved there. Another
class regarding shortcuts and default orientaiton will also be added.

BUG=366145
TBR=avi@chromium.org (for content/content.gyp)

Review URL: https://codereview.chromium.org/584523003

Cr-Commit-Position: refs/heads/master@{#295473}
13 files changed