Support extracting source mapping url defined by //@ sourceMappingURL=<url> comment.

src/mirror-debugger.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1764 matching lines @@
 ScriptMirror.prototype.id = function() {
   return this.script_.id;
 };
 
 
 ScriptMirror.prototype.source = function() {
   return this.script_.source;
 };
 
 
+ScriptMirror.prototype.sourceMappingURL = function() {
+  return this.script_.sourceMappingURL();
+};
+
+
 ScriptMirror.prototype.lineOffset = function() {
   return this.script_.line_offset;
 };
 
 
 ScriptMirror.prototype.columnOffset = function() {
   return this.script_.column_offset;
 };
 
 
@@ skipping 578 matching lines @@
   }
   if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }