Introduce KeepAliveWhilePending to ScriptPromiseResolverWithContext.

Source/modules/webmidi/NavigatorWebMIDI.h

Index: Source/modules/webmidi/NavigatorWebMIDI.h
diff --git a/Source/modules/webmidi/NavigatorWebMIDI.h b/Source/modules/webmidi/NavigatorWebMIDI.h
index 4e21441851ab20c93384535d67320658ac33f6c8..44337ff3825873b17dd938272f0cab7429aacaa1 100644
--- a/Source/modules/webmidi/NavigatorWebMIDI.h
+++ b/Source/modules/webmidi/NavigatorWebMIDI.h
@@ -33,26 +33,35 @@
 
 #include "bindings/v8/ScriptPromise.h"
 #include "core/frame/DOMWindowProperty.h"
+#include "modules/webmidi/MIDIAccessInitializer.h"
 #include "modules/webmidi/MIDIOptions.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
+#include "wtf/HashSet.h"
 
 namespace WebCore {
 
 class Navigator;
+class MIDIAccess;
 
-class NavigatorWebMIDI FINAL : public NoBaseWillBeGarbageCollectedFinalized<NavigatorWebMIDI>, public WillBeHeapSupplement<Navigator>, public DOMWindowProperty {
+class NavigatorWebMIDI FINAL : public NoBaseWillBeGarbageCollectedFinalized<NavigatorWebMIDI>, public WillBeHeapSupplement<Navigator>, public DOMWindowProperty, MIDIAccessInitializer::Client {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(NavigatorWebMIDI);
 public:
     virtual ~NavigatorWebMIDI();
     static NavigatorWebMIDI& from(Navigator&);
 
     static ScriptPromise requestMIDIAccess(ScriptState*, Navigator&, const Dictionary&);
-    ScriptPromise requestMIDIAccess(ScriptState*, const Dictionary&);
+
+    // MIDIAccessInitializer::Client implementaion
+    virtual void didFinishMIDIAccessInitialization(MIDIAccessInitializer*) OVERRIDE;
+    virtual void didFailMIDIAccessInitialization(MIDIAccessInitializer*) OVERRIDE;
 
     virtual void trace(Visitor* visitor) OVERRIDE { WillBeHeapSupplement<Navigator>::trace(visitor); }
 
 private:
+    ScriptPromise requestMIDIAccessInternal(ScriptState*, Navigator&, const Dictionary&);
+
+    HashSet<OwnPtr<MIDIAccessInitializer> > m_initializers;
     NavigatorWebMIDI(LocalFrame*);
     static const char* supplementName();
 };