exception log messages are duplicated

[devoncarew]

exceptions written to Console.log from WIP are duplicated. So doing something like int.parse("foo") throws an exception, but this is printed in the editor:

Exception: FormatException: abc
  int._native_parse (dart:core-patch/integers_patch.dart:54:3)
  int.parse (dart:core-patch/integers_patch.dart:59:59)
  reverseText (http://127.0.0.1:3030/Users/devoncarew/dart/polymer_test/web/polymer_test.dart:13:12)
Exception: FormatException: abc
  int._native_parse (dart:core-patch/integers_patch.dart:54:3)
  int.parse (dart:core-patch/integers_patch.dart:59:59)
  reverseText (http://127.0.0.1:3030/Users/devoncarew/dart/polymer_test/web/polymer_test.dart:13:12)

and here's what we receive from Dartium:

{"method":"Console.messageAdded","params":{"message":{"timestamp":1.376080711376144E9,"text":"Exception: FormatException: abc","level":"error","source":"javascript","column":3,"line":54,"repeatCount":1,"type":"log","url":"dart:core-patch/integers_patch.dart","stackTrace":[{"lineNu ... arew/dart/polymer_test/web/polymer_test.dart"}]}}}

{"method":"Console.messageRepeatCountUpdated","params":{"timestamp":1.376080711376884E9,"count":2}}

I don't think we should be getting a Console.messageRepeatCountUpdated message.

[jacob314]

Added Started label.

[jacob314]

Added Fixed label.