Convert enable_bidirectional_stream into build flag local to net.

net/http/bidirectional_stream.h

Index: net/http/bidirectional_stream.h
diff --git a/net/http/bidirectional_stream.h b/net/http/bidirectional_stream.h
index 14063fb0e47758ff6441e161caeb5855dd86a6d0..0cb3a15d3834706c46b951d09cb83330b6a9456b 100644
--- a/net/http/bidirectional_stream.h
+++ b/net/http/bidirectional_stream.h
@@ -14,10 +14,6 @@
 #include "net/http/http_stream_factory.h"
 #include "net/log/net_log.h"
 
-#if !defined(ENABLE_BIDIRECTIONAL_STREAM)
-#error Only include this if ENABLE_BIDIRECTIONAL_STREAM is defined

[Nico, 2015/12/30 22:36:21]

This is still important, else we'll get linker errors on bots building with
-frtti if someone includes this file without checking for the define.

[mef, 2015/12/30 23:20:46]

Ack, I'm open for suggestions.

[Nico, 2015/12/30 23:25:32]

"Don't remove this"? :-) What breaks if you keep it?

[mef, 2015/12/30 23:42:04]

Compilation of components/cronet because it has to include this file for
definition of BidirectionalStream::Delegate, yet it does not know about
net::ENABLE_BIDIRECTIONAL_STREAM build flag.

[mmenke, 2016/01/04 18:43:13]

The code to declare the build flag is a "public" dependency...  I assume that
means there's some way cronet can transitively access the build flag?  If not,
why is it a public and not a private dependency?

[mef, 2016/01/04 20:19:54]

Hrm, IIUIC move of enable_bidirectional_stream flag from base/common.gypi into
net.gypi made it essentially a private net/ flag and is not accessible from
other targets. 

I've added a separate cronet::enable_bidirectional_stream flag which doesn't
depend on net::enable_bidirectional_stream flag.

Is there some way to define a private dependency of
cronet::enable_bidirectional_stream on net::enable_bidirectional_stream flag?

-#endif
-
 class GURL;
 
 namespace net {