Make host_forwarder better handle duplicate forwards.

tools/android/forwarder2/host_forwarder_main.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <errno.h>
 #include <signal.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
@@ skipping 116 matching lines @@
       SendMessage(
           !removed_elements ? "ERROR: could not unmap port" : "OK",
           client_socket.get());
       return;
     }
     int host_port;
     if (!pickle_it.ReadInt(&host_port)) {
       SendMessage("ERROR: missing host port", client_socket.get());
       return;
     }
+    const bool use_dynamic_port_allocation = device_port == 0;
+    if (!use_dynamic_port_allocation) {
+      const std::string controller_key = MakeHostControllerMapKey(
+          adb_port, device_port);
+      LOG(INFO) << "Already forwarding device port " << device_port
+                << " to host port " << host_port;
+      if (controllers_.find(controller_key) != controllers_.end()) {
+        SendMessage(base::StringPrintf("%d:%d", device_port, host_port),
+                    client_socket.get());
+        return;
+      }
+    }
     // Create a new host controller.
     scoped_ptr<HostController> host_controller(
         new HostController(device_port, "127.0.0.1", host_port, adb_port,
                            GetExitNotifierFD()));
     if (!host_controller->Connect()) {
       has_failed_ = true;
       SendMessage("ERROR: Connection to device failed.", client_socket.get());
       return;
     }
     // Get the current allocated port.
@@ skipping 168 matching lines @@
 
   return client_delegate.has_failed() || daemon_delegate.has_failed();
 }
 
 }  // namespace
 }  // namespace forwarder2
 
 int main(int argc, char** argv) {
   return forwarder2::RunHostForwarder(argc, argv);
 }