DevTools: introduce object previews experiment

third_party/WebKit/LayoutTests/inspector/console/console-eval-exception-report-expected.txt

 Tests that evaluating an expression with an exception in the console provide correct exception information.
 
         function foo()
         {
             throw {a:239};
         }
         function boo()
         {
             foo();
         }
         boo();
-VM:3 Uncaught Object {a: 239}
+VM:3 Uncaught {a: 239}
 foo @ VM:3
 boo @ VM:7
 (anonymous) @ VM:9
 call frame:foo at :2
 call frame:boo at :6
 call frame: at :8