[Chromoting] Remove DataChannelManagerCallbacks constructor parameter of ClientSession

remoting/protocol/data_channel_manager.cc

Index: remoting/protocol/data_channel_manager.cc
diff --git a/remoting/protocol/data_channel_manager.cc b/remoting/protocol/data_channel_manager.cc
index c8f0782f38dafcef4d286a3b5bc5ed3d331bf49c..aa2914ed5ce4849f479a49ca0dfcbeccf00e74ab 100644
--- a/remoting/protocol/data_channel_manager.cc
+++ b/remoting/protocol/data_channel_manager.cc
@@ -20,7 +20,7 @@ void DataChannelManager::RegisterCreateHandlerCallback(
     CreateHandlerCallback constructor) {
   DCHECK(!prefix.empty());
   DCHECK(constructor);
-  constructors_.push_back(std::make_pair(prefix, constructor));
+  constructors_.push_back(std::make_pair(prefix, std::move(constructor)));

[jarhar, 2017/07/05 17:51:42]

just curious, what effect does using std::move have on the callback? Why was it
not needed before?

[Hzj_jie, 2017/07/05 18:34:31]

It does not impact the logic, but only the performance: Callback implements a
move constructor, so using it here can move its variables to avoid copying them
(bound objects).

So in general we should use std::move() to move Callback instances when passing
them into containers / functions. But we definitely missed most of them in the
entire Chromium.

I do not think in a short time, C++ will have an "automatic move" rule. So we
may need to take care of this issue for a long time.

 }
 
 bool DataChannelManager::OnIncomingDataChannel(