Extracting NetLog inner classes into their own classes.

net/spdy/spdy_header_block.h

Index: net/spdy/spdy_header_block.h
diff --git a/net/spdy/spdy_header_block.h b/net/spdy/spdy_header_block.h
index 6a24a4479645cfbd38047a3336a14999f58e948c..b0d57341cff81bf2a4f26e8e971dc36270225a4c 100644
--- a/net/spdy/spdy_header_block.h
+++ b/net/spdy/spdy_header_block.h
@@ -18,11 +18,17 @@
 #include "net/base/net_export.h"
 #include "net/log/net_log.h"
 
+namespace base {
+class Value;
+}
+
 namespace net {
 
 // Allows arg-dependent lookup to work for logging's operator<<.
 using ::operator<<;
 
+class NetLogCaptureMode;
+
 namespace test {
 class StringPieceProxyPeer;
 }