Teach the Observatory about WeakProperties (ephemerons).

runtime/bin/vmservice/observatory/deployed/web/index_devtools.html

Index: runtime/bin/vmservice/observatory/deployed/web/index_devtools.html
diff --git a/runtime/bin/vmservice/observatory/deployed/web/index_devtools.html b/runtime/bin/vmservice/observatory/deployed/web/index_devtools.html
index fc45ecfc9b580aa13721149a1e2d9171a95aadae..9caa13251c079d9c6b23c5380424d514424fd6e1 100644
--- a/runtime/bin/vmservice/observatory/deployed/web/index_devtools.html
+++ b/runtime/bin/vmservice/observatory/deployed/web/index_devtools.html
@@ -987,6 +987,26 @@ hr {
           </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>
@@ -15515,6 +15535,23 @@ hr {
             </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">