Switch to using SourceLocation universally in service protocol.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="library_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="script_ref.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="view_footer.html">
 
 <polymer-element name="field-view" extends="observatory-element">
@@ skipping 28 matching lines @@
       <div class="memberList">
         <div class="memberItem">
           <div class="memberName">owner</div>
           <div class="memberValue">
             <any-service-ref ref="{{ field.dartOwner }}"></any-service-ref>
           </div>
         </div>
         <div class="memberItem">
           <div class="memberName">script</div>
           <div class="memberValue">
-            <script-ref ref="{{ field.script }}"></script-ref>
+            <source-link location="{{ field.location }}"></source-link>
           </div>
         </div>
         <template if="{{ !field.isStatic }}">
           <div class="memberItem"
                title="The types observed for this field at runtime.  Fields that are observed to have a single type at runtime or to never be null may allow for additional optimization.">
             <div class="memberName">observed types</div>
             <div class="memberValue">
               <template if="{{ field.guardClass == 'dynamic' }}">
                 various
               </template>
@@ skipping 21 matching lines @@
             </div>
           </div>
         </template>
       </div>
     </div>
     <view-footer></view-footer>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="field_view.dart"></script>