Improve multi-process debugging.

mojo/shell/child_process_host.h

 // Copyright 2014 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.
 
 #ifndef SHELL_CHILD_PROCESS_HOST_H_
 #define SHELL_CHILD_PROCESS_HOST_H_
 
 #include "base/macros.h"
 #include "base/process/process.h"
 #include "mojo/edk/embedder/channel_info_forward.h"
@@ skipping 12 matching lines @@
 // child process. Currently runs a single app (loaded from the file system).
 //
 // This class is not thread-safe. It should be created/used/destroyed on a
 // single thread.
 //
 // Note: Does not currently work on Windows before Vista.
 // Note: After |Start()|, |StartApp| must be called and this object must
 // remained alive until the |on_app_complete| callback is called.
 class ChildProcessHost {
  public:
-  explicit ChildProcessHost(Context* context);
+  // |name| is just for debugging ease.
+  ChildProcessHost(Context* context, const std::string& name);
   virtual ~ChildProcessHost();
 
   // |Start()|s the child process; calls |DidStart()| (on the thread on which
   // |Start()| was called) when the child has been started (or failed to start).
   // After calling |Start()|, this object must not be destroyed until
   // |DidStart()| has been called.
   // TODO(vtl): Consider using weak pointers and removing this requirement.
   void Start();
 
   // Waits for the child process to terminate, and returns its exit code.
@@ skipping 14 matching lines @@
 
  private:
   bool DoLaunch();
 
   void AppCompleted(int32_t result);
 
   // Callback for |embedder::CreateChannel()|.
   void DidCreateChannel(embedder::ChannelInfo* channel_info);
 
   Context* const context_;
+  const std::string name_;
   base::Process child_process_;
   embedder::PlatformChannelPair platform_channel_pair_;
   ChildControllerPtr controller_;
   embedder::ChannelInfo* channel_info_;
   ChildController::StartAppCallback on_app_complete_;
 
   // Platform-specific "pipe" to the child process. Valid immediately after
   // creation.
   embedder::ScopedPlatformHandle platform_channel_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildProcessHost);
 };
 
 }  // namespace shell
 }  // namespace mojo
 
 #endif  // SHELL_CHILD_PROCESS_HOST_H_