Remove unused ExtraData support on exported mediastream objects.

public/platform/WebRTCVoidRequest.h

Index: public/platform/WebRTCVoidRequest.h
diff --git a/public/platform/WebRTCVoidRequest.h b/public/platform/WebRTCVoidRequest.h
index 192ce10565034247f2196de50454133c8c6b31ac..bcdff34efa1be36fc28b5c2e9af551c974738ce4 100644
--- a/public/platform/WebRTCVoidRequest.h
+++ b/public/platform/WebRTCVoidRequest.h
@@ -42,11 +42,6 @@ class RTCVoidRequest;
 
 class WebRTCVoidRequest {
 public:
-    class ExtraData {
-    public:
-        virtual ~ExtraData() { }
-    };
-
     WebRTCVoidRequest() { }
     WebRTCVoidRequest(const WebRTCVoidRequest& other) { assign(other); }
     ~WebRTCVoidRequest() { reset(); }
@@ -65,13 +60,6 @@ public:
     BLINK_PLATFORM_EXPORT void requestSucceeded() const;
     BLINK_PLATFORM_EXPORT void requestFailed(const WebString& error) const;
 
-    // Extra data associated with this object.
-    // If non-null, the extra data pointer will be deleted when the object is destroyed.
-    // Setting the extra data pointer will cause any existing non-null
-    // extra data pointer to be deleted.
-    BLINK_PLATFORM_EXPORT ExtraData* extraData() const;
-    BLINK_PLATFORM_EXPORT void setExtraData(ExtraData*);
-
 #if INSIDE_BLINK
     BLINK_PLATFORM_EXPORT WebRTCVoidRequest(RTCVoidRequest*);
 #endif