Add fuzzer-collapse-details-sk and demo

fuzzer/res/imp/fuzzer-stacktrace-sk.html

 <!--
   The common.js file must be included before this file.
 
   This in an HTML Import-able file that contains the definition
   of the following elements:
 
     <fuzzer-stacktrace-sk>
 
   <fuzzer-stacktrace-sk> displays a strack trace showing the first 8 frames and can be expanded with a click.
 
@@ skipping 110 matching lines @@
           return trace.frames;
         }
         return trace.frames.slice(0, 8);
       },
 
       showMore: function() {
         this.expanded = true;
         this.$.expand.toggleClass("hidden");
       }
     });
-  </script
-</dom-module id="fuzzer-stacktrace-sk">
+  </script>
+</dom-module>