Teach the Observatory about WeakProperties (ephemerons).

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

Index: runtime/bin/vmservice/observatory/lib/src/elements/instance_ref.html
diff --git a/runtime/bin/vmservice/observatory/lib/src/elements/instance_ref.html b/runtime/bin/vmservice/observatory/lib/src/elements/instance_ref.html
index 8bbcac5ed6979ada5fe256ad99880a00e548f30d..5f0757b1365d422ed09df17449d7dc02ff2c9a1b 100644
--- a/runtime/bin/vmservice/observatory/lib/src/elements/instance_ref.html
+++ b/runtime/bin/vmservice/observatory/lib/src/elements/instance_ref.html
@@ -70,6 +70,26 @@
           </div>
         </curly-block>
       </template>
+
+      <template if="{{ ref.isWeakProperty }}">
+        <a on-click="{{ goto }}" _href="{{ url }}"><em>{{ ref.clazz.name }}</em></a>
+        <curly-block callback="{{ expander() }}">
+          <div class="memberList">
+            <div class="memberItem">
+              <div class="memberName">key</div>
+              <div class="memberValue">
+                <any-service-ref ref="{{ ref.key }}"></any-service-ref>
+              </div>
+            </div>
+            <div class="memberItem">
+              <div class="memberName">value</div>
+              <div class="memberValue">
+                <any-service-ref ref="{{ ref.value }}"></any-service-ref>
+              </div>
+            </div>
+          </div>
+        </curly-block>
+      </template>
     </span>
   </template>
 </polymer-element>