Improve CPU Profile View

runtime/observatory/lib/src/elements/class_view.html

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="action_link.html">
 <link rel="import" href="cpu_profile.html">
 <link rel="import" href="curly_block.html">
 <link rel="import" href="eval_box.html">
 <link rel="import" href="eval_link.html">
 <link rel="import" href="field_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="library_ref.html">
@@ skipping 252 matching lines @@
             </div>
           </div>
         </template>
       </div>
       <sample-buffer-control id="sampleBufferControl"></sample-buffer-control>
       <br>
       <stack-trace-tree-config id="stackTraceTreeConfig"></stack-trace-tree-config>
       <br>
       <div class="flex-row centered">
         <div class="flex-item-90-percent outlined" style="margin: 16px; margin-left: 8px; margin-right: 8px">
-          <cpu-profile-tree id="cpuProfileTree"></cpu-profile-tree>
+          <cpu-profile-virtual-tree id="cpuProfileTree"></cpu-profile-virtual-tree>
         </div>
       </div>
     </div>
 
     <div class="content-centered-big">
       <hr>
       <source-inset location="{{ cls.location }}">
       </source-inset>
     </div>
 
     <view-footer></view-footer>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="class_view.dart"></script>