Added a net::BidirectionalStream to expose a bidirectional streaming interface

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 7403fe2a68de1550f33ec7d126d2a2d62af58d8b..375f6de801c8a823aee6a4cf99236e4dcca1564b 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -59,6 +59,9 @@ config("net_config") {
   if (disable_ftp_support) {
     defines += [ "DISABLE_FTP_SUPPORT=1" ]
   }
+  if (enable_bidirectional_stream) {
+    defines += [ "ENABLE_BIDIRECTIONAL_STREAM=1" ]
+  }
 }
 
 # net_internal_config is shared with net and net_small.