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

ui/keyboard/resources/elements/kb-keyset.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-keyset" attributes="nextKeyset isDefault"
     on-key-up="{{keyUp}}" on-key-longpress="{{keyLongpress}}">
   <template>
     <style>
       :host {
         -webkit-box-flex: 1;
         -webkit-box-orient: vertical;
         display: -webkit-box;
       }
+      :host:not(.activeKeyset) {
+        display: none;
+      }
     </style>
     <content select="kb-row"></content>
     <content select="kb-altkey-container" id="altkeyContainer"
         touch-action="none"></content>
     <kb-altkey-data id="altkeyMetadata"></kb-altkey-data>
   </template>
   <script>
     Polymer('kb-keyset', {
       isDefault: false,
       nextKeyset: undefined,
@@ skipping 44 matching lines @@
         activeAltKeySet.style.width = event.target.clientWidth *
             activeAltKeySet.childElementCount + 'px';
         activeAltKeySet.style.height = event.target.clientHeight + 'px';
         activeAltKeySet.style.top = event.target.offsetTop + 'px';
         var leftOffset = activeAltKeySet.offset * event.target.clientWidth;
         activeAltKeySet.style.left = event.target.offsetLeft - leftOffset +
             'px';
         var nodes = activeAltKeySet.childNodes;
         nodes[activeAltKeySet.offset].classList.add('active');
         altkeyContainer.hidden = false;
-      }
+      },
+
+      show: function() {
+        this.classList.add('activeKeyset');

[kevers, 2014/01/15 23:33:07]

Worth checking if you're already active.  This method could also take care of
hiding the previous keyset.

[rsadam, 2014/01/17 15:43:53]

Done.

+        this.fire('stateChange', {
+          state: 'keysetChanged',
+          value: this.id
+        });
+      },
+
+      hide: function() {
+        this.classList.remove('activeKeyset');
+      },
+
+      enteredView: function() {
+        // TODO(rsadam): Fix the stutter when a keyset is first loaded. Should
+        // be fixable after pixel perfect lands.
+        if (this.isDefault)

[kevers, 2014/01/15 23:33:07]

The stutter can be addressed by doing the equivalent of Polymer's veil/unveil. 
Simply add a class to the keyset that forces opacity to 0.  Once the keyset is
loaded and ready for display, pop off the "hide-me" class.

[rsadam, 2014/01/17 15:43:53]

Didn't have luck with veil/unveil. endOrMicroTask should suffice.

+          this.show();
+      },
     });
   </script>
 </polymer-element>