Revert 240681 "Revert 240536 "Mac-specific implementation of the..."

Reverting the revert: observed failures may have been red herrings.

> Revert 240536 "Mac-specific implementation of the GlobalShortcut..."
> 
> Reason for revert: patch suspected of causing flakiness on
> tests EventUtilsTest.TestEventFlagsFromNSEvent and
> EventUtilsTest.TestWindowOpenDispositionFromNSEvent on mac10.6 and
> mac 10.8 (ui_unit_tests on chromium.webkit waterfall)
> 
> > Mac-specific implementation of the GlobalShortcutListener class that
> > listens for global shortcuts. Handles basic keyboard intercepting and
> > forwards its output to the base class for processing.
> > 
> > Adds two things:
> > 1. Intercepts media keys. Uses an event tap for intercepting media keys
> > (PlayPause, NextTrack, PreviousTrack).
> > 2. Binds keyboard shortcuts (hot keys). Carbon RegisterEventHotKey API for
> > binding to non-media key global hot keys (eg. Command-Shift-1).
> > 
> > Also added Mac tests.
> > 
> > BUG=302437
> > 
> > Review URL: https://codereview.chromium.org/60353008
> 
> TBR=smus@chromium.org
> 
> Review URL: https://codereview.chromium.org/115323003

TBR=smus@chromium.org

Review URL: https://codereview.chromium.org/99133021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240915 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240915