Update SPDY4 length field to exclude frame prefix length.

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 44918e290c4a589ca9fd4a08d1bcf12d49ff781c..01de6600b2dc697f7d5576a3d5b4fa16290c4074 100644
--- a/net/spdy/spdy_framer.h
+++ b/net/spdy/spdy_framer.h
@@ -479,6 +479,9 @@ class NET_EXPORT_PRIVATE SpdyFramer {
   // Returns the maximum size a frame can be (data or control).
   size_t GetFrameMaximumSize() const;
 
+  // Returns the maximum size that a control frame can be.
+  size_t GetControlFrameMaximumSize() const;
+
   // Returns the maximum payload size of a DATA frame.
   size_t GetDataFrameMaximumPayload() const;