Reverting this CL because it was committed before I gave the final LGTM.

Reverting this CL because it was committed before I gave the final LGTM.

Revert 162142 - Full Screen Magnifier: Add MagnificationManager

MagnificationManager controls the full screen magnifier from chrome-browser side (not ash side. Note that MagnificationController is on ash side).

MagnificationManager does:
- Watch logged-in. Change the behavior between the login screen and user desktop. 
- Watch change of the pref. When the pref changes, the setting of the magnifier will interlock with it.

In addition, this patch make the magnifier settings per-user instead of per-device.

BUG=151891
TEST=manual, browser_test passes.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=162080

Review URL: https://chromiumcodereview.appspot.com/11065008

TBR=yoshiki@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=162211