Revert 176102

Revert 176102
The revert didn't fix the ChromeOS failures so I'm restoring the change.
> Revert 176087
> 
> Appears to break ChromeOS browser_tests.
> 
> > Re-introduce the partial magnifier
> > 
> > Major Changes:
> > - Adding a selectbox at the right of screen magnifier setting on the setting page.
> > - Adding 'screen_magnifier_type2' pref.
> > - Separating the enable/disable state of magnifier from MagnifierType. MagnifierType does no longer indicate the current enable/disable status.
> > - Add IsMagnifierEnabled() to shell delegate.
> > 
> > BUG=166832
> > TEST=confirm that magnifier can be enabled/disabled via the tray and the settings page. browser_test passes.
> > 
> > R=zork@chromium.org, derat@chromium.org, nkostylev@chromium.org
> > TBR=jhawkins@chromium.org
> > # TBRing for small changed in C/B/ui/webui/options/ and C/B/resources/options/
> > 
> > Review URL: https://chromiumcodereview.appspot.com/11642014
> 
> TBR=yoshiki@chromium.org
> Review URL: https://codereview.chromium.org/11821053

TBR=acolwell@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=176111