Switch to using SourceLocation universally in service protocol.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="action_link.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="isolate_ref.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 <polymer-element name="isolate-summary" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
@@ skipping 65 matching lines @@
       <template if="{{ isolate.pauseEvent.kind == 'PauseInterrupted' ||
                        isolate.pauseEvent.kind == 'PauseBreakpoint' ||
                        isolate.pauseEvent.kind == 'PauseException' }}">
         <template if="{{ isolate.pauseEvent.breakpoint != null }}">
           by breakpoint
         </template>
         <template if="{{ isolate.pauseEvent.kind == 'PauseException' }}">
           by exception
         </template>
         at
-        <function-ref ref="{{ isolate.topFrame['function'] }}">
+        <function-ref ref="{{ isolate.topFrame.function }}">
         </function-ref>
-        (<script-ref ref="{{ isolate.topFrame['script'] }}"
-                     pos="{{ isolate.topFrame['tokenPos'] }}"></script-ref>)
+        (<source-link location="{{ isolate.topFrame.location }}">
+        </source-link>)
       </template>
     </template>
 
     <template if="{{ isolate.running }}">
       at
-      <function-ref ref="{{ isolate.topFrame['function'] }}">
+      <function-ref ref="{{ isolate.topFrame.function }}">
       </function-ref>
-      (<script-ref ref="{{ isolate.topFrame['script'] }}"
-                   pos="{{ isolate.topFrame['tokenPos'] }}"></script-ref>)
+      (<source-link location="{{ isolate.topFrame.location }}"></source-link>)
     </template>
 
   </template>
 </polymer-element>
 
 <polymer-element name="isolate-shared-summary" extends="observatory-element">
   <template>
     <style>
       .errorBox {
         background-color: #f5f5f5;
@@ skipping 94 matching lines @@
   </template>
 </polymer-element>
 
 <polymer-element name="isolate-counter-chart" extends="observatory-element">
   <template>
     <div id="counterPieChart" style="height: 200px"></div>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="isolate_summary.dart"></script>