Add callers and callees to profiler output

runtime/bin/vmservice/client/lib/src/observatory_elements/table_tree.html

+<link rel="import" href="observatory_element.html">
+<polymer-element name="table-tree" extends="observatory-element">
+  <template>
+    <div class="row">
+      <div class="col-md-12">
+        <table class="table table-hover" id="_table">
+          <thead>
+            <tr>
+              <template repeat="{{ header in tree.columnHeaders }}">
+                <th>{{header}}</th>
+              </template>
+            </tr>
+          </thead>
+          <tbody>
+            <tr template repeat="{{row in tree.rows }}" style="{{}}">
+              <td on-click="{{toggleExpanded}}"
+                  class="{{ coloring(row) }}"
+                  style="{{ padding(row) }}">
+                {{row.columns[0]}}
+              </td>
+              <template repeat="{{ col in row.columns.skip(1) }}">
+                <td class="{{ coloring(row) }}">{{col}}</td>
+              </template>
+            </tr>
+          </tbody>
+        </table>
+      </div>
+    </div>
+  </template>
+  <script type="application/dart" src="table_tree.dart"></script>
+</polymer-element>