Work around for content select not supporting touch events on it's children.

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

 <!--
   -- Copyright 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-key" extends="kb-key-base"
     attributes="image imageSize keyCode keyName shiftModifier weight">
   <template>
     <style>
@@ skipping 134 matching lines @@
       },
 
       /**
        * Adjusts the CSS rules for rendering the key to reflect the new
        * weight. The preferred way is to use {{weight}} directly in the CSS
        * rules; however, this is currently broken in the Polymer library.
        * TODO(kevers): Cleanup once handling of {{}} in CSS rules is fixed.
        */
       weightChanged: function() {
         if (this.weight > 0)
-          this.style['webkitBoxFlex'] = this.weight;
+          this.style.webkitBoxFlex = this.weight;
       },
     });
   </script>
 </polymer-element>
 
 <!-- Special keys -->
 <polymer-element name="kb-abc-key" class="symbol dark" char="Invalid"
     extends="kb-key" weight="125">
   <script>
     Polymer('kb-abc-key', {
@@ skipping 47 matching lines @@
       up: function(event) {
         if (this.longPressTimer) {
           clearTimeout(this.longPressTimer);
           hideKeyboard();
           this.longPressTimer = undefined;
         }
       }
     });
   </script>
 </polymer-element>