Implement 'print', 'up', 'down', and 'frame' commands in the Observatory debugger.

runtime/observatory/lib/src/elements/debugger.html

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 
 <!-- TODO(turnidge): Use core-icon once core_elements work properly in
      devtools -->
 <polymer-element name="icon-expand-less" noscript>
@@ skipping 173 matching lines @@
         padding: 5px;
         border: 1px solid white;
       }
       .frameOuter:hover {
         border: 1px solid #e0e0e0;
       }
       .shadow {
         box-shadow:  0 2px 10px 0 rgba(0, 0, 0, 0.16),
                      0 2px 5px 0 rgba(0, 0, 0, 0.26);
       }
+      .current {
+        box-shadow:  0 2px 10px 0 rgba(0, 0, 0, 0.26),
+                     0 2px 5px 0 rgba(0, 0, 0, 0.46);
+        border: 1px solid #444;
+      }
       .frameSummaryText {
         display: inline-block;
         padding: 5px;
       }
       .frameId {
         display: inline-block;
         width: 60px;
       }
       .frameOuter .frameExpander {
         position: absolute;
@@ skipping 104 matching lines @@
         margin: 20px;
         font: 400 16px consolas, courier, monospace;
         width: 95%;
       }
     </style>
     <input id="textBox" class="textBox" type="text" value="{{ text }}" autofocus>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="debugger.dart"></script>