Move TimezoneSettings::Observer -> SystemClockObserver

BUG=270135
R=derat@chromium.org

Review URL: https://codereview.chromium.org/26959007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228726 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228726
Add a metric to track the control events on the keyboard.

This differentiates between automatic hiding and user-initiated hiding.

BUG=302528

TEST=Show and hide the keyboard a few times by focusing and unfocusing text. Also, hide the keyboard once by pressing the hide keyboard button. Go to about:histograms and ensure that "VirtualKeyboard.KeyboardControlEvents" appears with event 0 being the number of times the keyboard was shown, event 1 being the number of times the keyboard was automatically hidden, and event 2 being the number of times a keyboard was manually hidden.

Review URL: https://codereview.chromium.org/25548002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228727 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228727