Implement virtual keyboard hiding.

ui/keyboard/resources/elements/kb-keyboard.html

 <!--
   -- Copyright (c) 2013 The Chromium Authors. All rights reserved.
   -- Use of this source code is governed by a BSD-style license that can be
   -- found in the LICENSE file.
   -->
 
 <polymer-element name="kb-keyboard" on-key-over="keyOver" on-key-up="keyUp"
     on-key-down="keyDown" on-key-longpress="keyLongpress" on-pointerup="up"
     on-enable-dbl="enableDbl" attributes="keyset layout rows">
   <template>
@@ skipping 198 matching lines @@
         var toKeyset = detail.toKeyset;
         // Keyset transition key.
         if (toKeyset) {
           this.keyset = toKeyset;
           this.querySelector('#' + this.layout + '-' + this.keyset).nextKeyset =
               detail.nextKeyset;
         }
         var toLayout = detail.toLayout;
         // Layout transition key.
         if (toLayout)
-          this.layout = toLayout;
+          hideKeyboard();
         var char = detail.char;
         if (enterUpperOnSpace) {
           enterUpperOnSpace = false;
           if (char == ' ')
             this.keyset = 'upper';
         }
         switch(char) {
           case 'Invalid':
           case 'Shift':
             return;
@@ skipping 68 matching lines @@
           }
         }
         if (keysetsLoaded)
           console.error('No default keyset found for ' + this.layout);
         return false;
       }
     });
   </script>
 </polymer-element>