Use JSON.stringify to serialize debugger messages

test/mjsunit/mirror-number.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 number values
 
 function testNumberMirror(n) {
   // Create mirror and JSON representation.
   var mirror = debug.MakeMirror(n);
   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);
   assertTrue(mirror instanceof debug.ValueMirror);
   assertTrue(mirror instanceof debug.NumberMirror);
 
   // Check the mirror properties.
   assertTrue(mirror.isNumber());
   assertEquals('number', mirror.type());
   assertTrue(mirror.isPrimitive());
@@ skipping 22 matching lines @@
 
 // Test a number of different numbers.
 testNumberMirror(-7);
 testNumberMirror(-6.5);
 testNumberMirror(0);
 testNumberMirror(42);
 testNumberMirror(100.0002);
 testNumberMirror(Infinity);
 testNumberMirror(-Infinity);
 testNumberMirror(NaN);