Teach the Observatory about WeakProperties (ephemerons).

runtime/bin/vmservice/observatory/lib/src/elements/instance_view.html

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
 <link rel="import" href="error_view.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="inbound_reference.html">
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="observatory_element.html">
@@ skipping 61 matching lines @@
           <template if="{{ instance.isClosure }}">
             <div class="memberItem">
               <div class="memberName">closure context</div>
               <div class="memberValue">
                 <any-service-ref ref="{{ instance.closureCtxt }}">
                 </any-service-ref>
               </div>
             </div>
           </template>
 
+          <template if="{{ instance.isWeakProperty }}">
+            <div class="memberItem">
+              <div class="memberName">key</div>
+              <div class="memberValue">
+                <any-service-ref ref="{{ instance.key }}">
+                </any-service-ref>
+              </div>
+            </div>
+            <div class="memberItem">
+              <div class="memberName">value</div>
+              <div class="memberValue">
+                <any-service-ref ref="{{ instance.value }}">
+                </any-service-ref>
+              </div>
+            </div>
+          </template>
+
           <div class="memberItem">
             <div class="memberName">toString()</div>
             <div class="memberValue">
               <eval-link callback="{{ eval }}" expr="toString()"></eval-link>
             </div>
           </div>
         </div>
       </div>
 
       <hr>
@@ skipping 55 matching lines @@
       </div>
 
       <br><br><br><br>
       <br><br><br><br>
 
     </template>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="instance_view.dart"></script>