Use JSON.stringify to serialize debugger messages

test/mjsunit/mirror-script.js

 // Copyright 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 14 matching lines @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --expose-debug-as debug
 // Test the mirror object for scripts.
 
 function testScriptMirror(f, file_name, file_lines, script_type, script_source) {
   // Create mirror and JSON representation.
   var mirror = debug.MakeMirror(f).script();
   var serializer = debug.MakeMirrorSerializer();
-  var json = serializer.serializeValue(mirror);
+  var json = JSON.stringify(serializer.serializeValue(mirror));
 
   // Check the mirror hierachy.
   assertTrue(mirror instanceof debug.Mirror);
   assertFalse(mirror instanceof debug.ValueMirror);
   assertTrue(mirror instanceof debug.ScriptMirror);
 
   // Check the mirror properties.
   assertTrue(mirror.isScript());
   assertEquals('script', mirror.type());
   var name = mirror.name();
@@ skipping 37 matching lines @@
 testScriptMirror(eval('function(){\n  }'), null, 2, 2, 'function(){\n  }');
 
 // Test taking slices of source.
 var mirror = debug.MakeMirror(eval('function(){\n  1;\n}')).script();
 assertEquals('function(){\n', mirror.sourceSlice(0, 1).sourceText());
 assertEquals('  1;\n', mirror.sourceSlice(1, 2).sourceText());
 assertEquals('}', mirror.sourceSlice(2, 3).sourceText());
 assertEquals('function(){\n  1;\n', mirror.sourceSlice(0, 2).sourceText());
 assertEquals('  1;\n}', mirror.sourceSlice(1, 3).sourceText());
 assertEquals('function(){\n  1;\n}', mirror.sourceSlice(0, 3).sourceText());