mac/linux: rework plugin channel file descriptor creation

chrome/plugin/plugin_channel.h

 // Copyright (c) 2006-2008 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 CHROME_PLUGIN_PLUGIN_CHANNEL_H_
 #define CHROME_PLUGIN_PLUGIN_CHANNEL_H_
 
 #include <vector>
 #include "base/scoped_handle.h"
 #include "build/build_config.h"
 #include "chrome/plugin/plugin_channel_base.h"
 #include "chrome/plugin/webplugin_delegate_stub.h"
 
 // Encapsulates an IPC channel between the plugin process and one renderer
 // process.  On the renderer side there's a corresponding PluginChannelHost.
 class PluginChannel : public PluginChannelBase {
  public:
   // Get a new PluginChannel object for the current process.
   // POSIX only: If |channel_fd| > 0, use that file descriptor for the
   // channel socket.
   static PluginChannel* GetPluginChannel(int process_id,
-                                         MessageLoop* ipc_message_loop,
-                                         int channel_fd);
+                                         MessageLoop* ipc_message_loop);
 
   ~PluginChannel();
 
   virtual bool Send(IPC::Message* msg);
   virtual void OnMessageReceived(const IPC::Message& message);
 
   base::ProcessHandle renderer_handle() const { return renderer_handle_; }
   int GenerateRouteID();
 
+#if defined(OS_POSIX)
+  // When first created, the PluginChannel gets assigned the file descriptor
+  // for the renderer.
+  // After the first time we pass it through the IPC, we don't need it anymore,
+  // and we close it. At that time, we reset renderer_fd_ to -1.
+  int DisownRendererFd() {
+    int value = renderer_fd_;
+    renderer_fd_ = -1;
+    return value;
+  }
+#endif
+
   bool in_send() { return in_send_ != 0; }
 
   bool off_the_record() { return off_the_record_; }
   void set_off_the_record(bool value) { off_the_record_ = value; }
 
  protected:
   // IPC::Channel::Listener implementation:
   virtual void OnChannelConnected(int32 peer_pid);
   virtual void OnChannelError();
 
   virtual void CleanUp();
 
+  // Overrides PluginChannelBase::Init.
+  virtual bool Init(MessageLoop* ipc_message_loop, bool create_pipe_now);
+
  private:
   // Called on the plugin thread
   PluginChannel();
 
   void OnControlMessageReceived(const IPC::Message& msg);
 
   static PluginChannelBase* ClassFactory() { return new PluginChannel(); }
 
   void OnCreateInstance(const std::string& mime_type, int* instance_id);
   void OnDestroyInstance(int instance_id, IPC::Message* reply_msg);
   void OnGenerateRouteID(int* route_id);
 
   std::vector<scoped_refptr<WebPluginDelegateStub> > plugin_stubs_;
 
   // Handle to the renderer process who is on the other side of the channel.
   base::ProcessHandle renderer_handle_;
 
+#if defined(OS_POSIX)
+  // FD for the renderer end of the pipe. It is stored until we send it over
+  // IPC after which it is cleared. It will be closed by the IPC mechanism.
+  int renderer_fd_;
+#endif
+
   int in_send_;  // Tracks if we're in a Send call.
   bool log_messages_;  // True if we should log sent and received messages.
   bool off_the_record_; // True if the renderer is in off the record mode.
 
   DISALLOW_EVIL_CONSTRUCTORS(PluginChannel);
 };
 
 #endif  // CHROME_PLUGIN_PLUGIN_CHANNEL_H_