Add a SpdyFramer extension API implementation.

net/spdy/spdy_frame_builder.cc

Index: net/spdy/spdy_frame_builder.cc
diff --git a/net/spdy/spdy_frame_builder.cc b/net/spdy/spdy_frame_builder.cc
index 172f9d2ab6ce7825a0ec3d212f35ec4f0e9a5cc6..bb13e60d018cba7f3002077d03dbb6d2f46c99a3 100644
--- a/net/spdy/spdy_frame_builder.cc
+++ b/net/spdy/spdy_frame_builder.cc
@@ -125,12 +125,10 @@ bool SpdyFrameBuilder::BeginNewFrame(const SpdyFramer& framer,
 }
 
 bool SpdyFrameBuilder::BeginNewFrame(const SpdyFramer& framer,
-                                     SpdyFrameType type,
+                                     uint8_t raw_frame_type,
                                      uint8_t flags,
                                      SpdyStreamId stream_id,
                                      size_t length) {
-  uint8_t raw_frame_type = SerializeFrameType(type);
-  DCHECK(IsDefinedFrameType(raw_frame_type));
   DCHECK_EQ(0u, stream_id & ~kStreamIdMask);
   bool success = true;
   SPDY_BUG_IF(framer.GetFrameMaximumSize() < length_)