Upstream accessibility font size preferences.
Moves ForceEnableZoom, UserSetForceEnableZoom, and
FontScaleFactor preferences upstream and adds support for
observing all those preferences in Java.
UserSetForceEnableZoom is currently stored using Android
SharedPreferences, which are application global, so this
class is currently not keyed off the profile. Preferably
this should be migrated to be per profile, at which point
the FontSizePrefs could be keyed off the profile instead of
being an application global singleton.
BUG=383630
Review URL: https://codereview.chromium.org/
415343002
Cr-Commit-Position: refs/heads/master@{#289185}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289185 0039d316-1c4b-4281-b951-d872f2087c98