Remove unused ExtraData support on exported mediastream objects.

public/platform/WebRTCSessionDescriptionRequest.h

Index: public/platform/WebRTCSessionDescriptionRequest.h
diff --git a/public/platform/WebRTCSessionDescriptionRequest.h b/public/platform/WebRTCSessionDescriptionRequest.h
index 77648fea49609790beceab629e9d93ea1fe450f2..cdf5d0e784b5da62851552214df1cc69d10f20d4 100644
--- a/public/platform/WebRTCSessionDescriptionRequest.h
+++ b/public/platform/WebRTCSessionDescriptionRequest.h
@@ -43,11 +43,6 @@ class WebRTCSessionDescription;
 
 class WebRTCSessionDescriptionRequest {
 public:
-    class ExtraData {
-    public:
-        virtual ~ExtraData() { }
-    };
-
     WebRTCSessionDescriptionRequest() { }
     WebRTCSessionDescriptionRequest(const WebRTCSessionDescriptionRequest& other) { assign(other); }
     ~WebRTCSessionDescriptionRequest() { reset(); }
@@ -66,13 +61,6 @@ public:
     BLINK_PLATFORM_EXPORT void requestSucceeded(const WebRTCSessionDescription&) 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 WebRTCSessionDescriptionRequest(RTCSessionDescriptionRequest*);
 #endif