IPC: Fix attachment brokering race condition.

ipc/ipc_channel_proxy.h

Index: ipc/ipc_channel_proxy.h
diff --git a/ipc/ipc_channel_proxy.h b/ipc/ipc_channel_proxy.h
index 2c5ec98e43a8a6c9e34878b82675df627b31900d..0c9323304098c2fc18c75f247479a749b1d3f27b 100644
--- a/ipc/ipc_channel_proxy.h
+++ b/ipc/ipc_channel_proxy.h
@@ -97,6 +97,11 @@ class IPC_EXPORT ChannelProxy : public Endpoint, public base::NonThreadSafe {
       Listener* listener,
       const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner);
 
+  // Constructs a ChannelProxy without initializing it.
+  ChannelProxy(
+      Listener* listener,
+      const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner);
+
   ~ChannelProxy() override;
 
   // Initializes the channel proxy. Only call this once to initialize a channel
@@ -159,9 +164,6 @@ class IPC_EXPORT ChannelProxy : public Endpoint, public base::NonThreadSafe {
   // to the internal state.
   ChannelProxy(Context* context);
 
-  ChannelProxy(
-      Listener* listener,
-      const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner);
 
   // Used internally to hold state that is referenced on the IPC thread.
   class Context : public base::RefCountedThreadSafe<Context>,