Incoming references service request and UI.

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

+<link rel="import" href="../../../../packages/polymer/polymer.html">
+<link rel="import" href="curly_block.html">
+<link rel="import" href="observatory_element.html">
+<link rel="import" href="service_ref.html">
+
+<polymer-element name="inbound-reference" extends="service-ref">
+  <template>
+    <link rel="stylesheet" href="css/shared.css">
+    <style>
+      .errorBox {
+        background-color: #f5f5f5;
+        border: 1px solid #ccc;
+        padding: 10px;
+        font-family: consolas, courier, monospace;
+        font-size: 1em;
+        line-height: 1.2em;
+        white-space: pre;
+      }
+    </style>
+    <div>
+      from <any-service-ref ref="{{ source }}"></any-service-ref>
+      <template if="{{ slotIsArrayIndex }}">via [{{ slot }}]</template>
+      <template if="{{ slotIsField }}">via <field-ref ref="{{ slot }}"></template>
+
+      <curly-block callback="{{ expander() }}">
+        <div class="memberList">
+          <div class="memberItem">
+            <div class="memberName">
+              <template repeat="{{ reference in inboundReferences] }}">
+                <inbound-reference ref="{{ reference }}"></inbound-reference>
+              </template>
+            </div>
+          </div>
+        </div>
+      </curly-block>
+    </div>
+  </template>
+</polymer-element>
+
+<script type="application/dart" src="inbound_reference.dart"></script>