Introduce Google Suggest Request Id - gs_ri parameter in suggest requests to Google search engine. This allows for introducing new suggestion types without causing bad interactions with older versions of chrome.

The suggest request parameters will be as follows in the newer versions of Chrome:
Android Mobile: client=chrome&gs_ri=chrome-mobile-ext
Desktop and Android Tablet: client=chrome-omni&gs_ri=chrome-ext

The older versions of chrome will not specify gs_ri.

BUG=328113
TBR=pkasting

Review URL: https://codereview.chromium.org/101953006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240988 0039d316-1c4b-4281-b951-d872f2087c98
Adds UMA stats for the search button in omnibox experiment.

BUG=304859, 315944
TBR=pkasting@chromium.org

Review URL: https://codereview.chromium.org/115593002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240989 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240989