Decouple MIDIAccess initialization from MIDIAccess class.

public/web/WebMIDIPermissionRequest.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
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  * modification, are permitted provided that the following conditions are
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@@ skipping 14 matching lines @@
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  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 #ifndef WebMIDIPermissionRequest_h
 #define WebMIDIPermissionRequest_h
 
 #include "../platform/WebCommon.h"
-#include "../platform/WebPrivatePtr.h"
 
 namespace WebCore {
-class MIDIAccess;
+class MIDIAccessInitializer;
 }
 
 namespace blink {
 
 class WebSecurityOrigin;
 
-// WebMIDIPermissionRequest encapsulates a WebCore MIDIAccess object and represents
-// a request from WebCore for permissions.
-// The underlying MIDIAccess object is guaranteed to be valid until the invocation of
+// WebMIDIPermissionRequest encapsulates a WebCore MIDIAccessInitializer
+// object and represents a request from WebCore for permissions.
+// The underlying object is guaranteed to be valid until the invocation of
 // either WebMIDIPermissionRequest::setIsAllowed (request complete) or
 // WebMIDIClient::cancelPermissionRequest (request canceled).
 class WebMIDIPermissionRequest {
 public:
-    WebMIDIPermissionRequest(const WebMIDIPermissionRequest& o) { assign(o); }
-    ~WebMIDIPermissionRequest() { reset(); };
-
+    BLINK_EXPORT WebMIDIPermissionRequest(const WebMIDIPermissionRequest& other)
+        : m_initializer(other.m_initializer) { }
     BLINK_EXPORT WebSecurityOrigin securityOrigin() const;
     BLINK_EXPORT void setIsAllowed(bool);
 
-    BLINK_EXPORT void reset();
-    BLINK_EXPORT void assign(const WebMIDIPermissionRequest&);
     BLINK_EXPORT bool equals(const WebMIDIPermissionRequest&) const;
 
 #if BLINK_IMPLEMENTATION
-    explicit WebMIDIPermissionRequest(const PassRefPtrWillBeRawPtr<WebCore::MIDIAccess>&);
+    explicit WebMIDIPermissionRequest(WebCore::MIDIAccessInitializer*);
 
-    WebCore::MIDIAccess* midiAccess() const { return m_private.get(); }
+    WebCore::MIDIAccessInitializer* midiAccessInitializer() const { return m_initializer; }
 #endif
 
 private:
-    WebPrivatePtr<WebCore::MIDIAccess> m_private;
+    WebCore::MIDIAccessInitializer* m_initializer;

[Takashi Toyoshima, 2014/06/04 22:03:53]

Can we ensure that m_initializer continues to be valid while
WebMIDIPermissionRequest is alive?
It will be related to my question on PassRefPtrWillBeRawPtr<>.

[yhirano, 2014/06/05 11:35:25]

I updated the class comment: is it clear now?

[tkent, 2014/06/10 04:28:31]

I don't understand how it is ensured.
This looks very easy to cause use-after-free. No one clears m_initializer and
WebMIDIPermissionRequest is copyable.

 };
 
 inline bool operator==(const WebMIDIPermissionRequest& a, const WebMIDIPermissionRequest& b)
 {
     return a.equals(b);
 }
 
 inline bool operator!=(const WebMIDIPermissionRequest& a, const WebMIDIPermissionRequest& b)
 {
     return !(a == b);
 }
 
 } // namespace blink
 
 #endif // WebMIDIPermissionRequest_h