Add a SpdyFramer extension API implementation.

net/spdy/spdy_framer.h

Index: net/spdy/spdy_framer.h
diff --git a/net/spdy/spdy_framer.h b/net/spdy/spdy_framer.h
index c8a5393e3624facbc4a1e69f6372efa4f148644b..c52b3899e187abe4bd6c975c0eebe83eae392916 100644
--- a/net/spdy/spdy_framer.h
+++ b/net/spdy/spdy_framer.h
@@ -213,6 +213,18 @@ class NET_EXPORT_PRIVATE SpdyFramerVisitorInterface {
   virtual bool OnUnknownFrame(SpdyStreamId stream_id, uint8_t frame_type) = 0;
 };
 
+class SpdyFrameSequence {
+ public:
+  virtual ~SpdyFrameSequence() {}
+
+  // Serializes the next frame in the sequence to |output|. Returns the number
+  // of bytes written to |output|.
+  virtual size_t NextFrame(ZeroCopyOutputBuffer* output) = 0;
+
+  // Returns true iff there is at least one more frame in the sequence.
+  virtual bool HasNextFrame() const = 0;
+};
+
 class ExtensionVisitorInterface {
  public:
   virtual ~ExtensionVisitorInterface() {}