Support finch experiment WebRTC-UDPServerSocketAsync for Windows.

content/browser/renderer_host/p2p/socket_host_udp.cc

Index: content/browser/renderer_host/p2p/socket_host_udp.cc
diff --git a/content/browser/renderer_host/p2p/socket_host_udp.cc b/content/browser/renderer_host/p2p/socket_host_udp.cc
index fd09f7d30534e890287c0e9ee94c614813199351..1548f1508ad3ec755fd89c208e4499485b6b0ae5 100644
--- a/content/browser/renderer_host/p2p/socket_host_udp.cc
+++ b/content/browser/renderer_host/p2p/socket_host_udp.cc
@@ -109,6 +109,14 @@ bool P2PSocketHostUdp::Init(const net::IPEndPoint& local_address,
                             const P2PHostAndIPEndPoint& remote_address) {
   DCHECK_EQ(state_, STATE_UNINITIALIZED);
 
+#if defined(OS_WIN)
+  // If configured for finch experiment, use nonblocking IO.
+  if (base::FieldTrialList::FindFullName("WebRTC-UDPServerSocketAsync") ==

[Sergey Ulanov, 2015/03/13 18:28:51]

This is not a good name for the experiment: overlapped IO that is used by
default is asynchronous too. Also you don't need to call them "ServerSocket".
They are just UDP sockets. I would suggest "WebRTC-UDPSocketNonBlockingIO". It's
still a bit ambiguous, but at least it's more consistent with the code.

[John L. Miller, 2015/03/23 14:11:27]

Done.

[John L. Miller, 2015/03/23 14:11:28]

Done.

+      "Enabled") {
+    static_cast<UdpServerSocket *>(socket_.get())->UseNonBlockingIO();

[Sergey Ulanov, 2015/03/13 18:28:51]

You can avoid upcast if you put this in the constructor (socket_ initialization
would need to be moved to the constructor body, out of the initializer list)

[John L. Miller, 2015/03/23 14:11:28]

I'm nervous about changing the type when socket_ is used many other places.
Going to leave this way if that's OK.

[Sergey Ulanov, 2015/03/25 17:50:28]

I wasn't suggesting to change type of |socket_|. I'm just saying you can avoid
this upcast by moving this code in the constructor. So in the construction you
would have something like this:

net::UDPServerSocket* socket = new net::UDPServerSocket(...);
socket_ = socket;
if (experiment enabled) {
 socket->UseNonBlockingIO();
}

+  }
+#endif
+
   int result = socket_->Listen(local_address);
   if (result < 0) {
     LOG(ERROR) << "bind() failed: " << result;