Have DOMWindow deal with references instead of pointers when possible

Source/modules/webmidi/MIDIOutput.cpp

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 27 matching lines @@
 #include "core/timing/Performance.h"
 #include "modules/webmidi/MIDIAccess.h"
 
 namespace WebCore {
 
 namespace {
 
 double now(ExecutionContext* context)
 {
     DOMWindow* window = context ? context->executingWindow() : 0;
-    Performance* performance = window ? window->performance() : 0;
+    Performance* performance = window ? &window->performance() : 0;
     return performance ? performance->now() : 0.0;
 }
 
 class MessageValidator {
 public:
     static bool validate(Uint8Array* array, ExceptionState& exceptionState, bool sysExEnabled)
     {
         MessageValidator validator(array);
         return validator.process(exceptionState, sysExEnabled);
     }
@@ skipping 171 matching lines @@
 {
     send(unsignedData, 0.0, exceptionState);
 }
 
 void MIDIOutput::trace(Visitor* visitor)
 {
     MIDIPort::trace(visitor);
 }
 
 } // namespace WebCore