Remove use of libcros from InputMethodLibrary.

BUG=chromium-os:16238
TEST==confirm that input methods work as before on the netbook. Also confirm that the chrome builds and works on the desktop as before.

Review URL: http://codereview.chromium.org/7003086

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@89142 0039d316-1c4b-4281-b951-d872f2087c98
   virtual std::string GetKeyboardOverlayId(const std::string& input_method_id) {
     if (!initialized_successfully_)
       return "";
 
    return input_method::GetKeyboardOverlayId(input_method_id);
   }

   virtual std::string GetKeyboardOverlayId(const std::string& input_method_id) {
     if (!initialized_successfully_)
       return "";
 
    return chromeos::GetKeyboardOverlayId(input_method_id);
   }
