mac/linux: rework plugin channel file descriptor creation

chrome/plugin/plugin_channel.h

Index: chrome/plugin/plugin_channel.h
diff --git a/chrome/plugin/plugin_channel.h b/chrome/plugin/plugin_channel.h
index 21373fb3e0361774518064fab64de5d3f967cf61..02b619e37a08c8b31a9ce302d85f090ea6372a25 100644
--- a/chrome/plugin/plugin_channel.h
+++ b/chrome/plugin/plugin_channel.h
@@ -19,8 +19,7 @@ class PluginChannel : public PluginChannelBase {
   // 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();
 
@@ -30,6 +29,18 @@ class PluginChannel : public PluginChannelBase {
   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_; }
@@ -42,6 +53,9 @@ class PluginChannel : public PluginChannelBase {
 
   virtual void CleanUp();
 
+  // Overrides PluginChannelBase::Init.
+  virtual bool Init(MessageLoop* ipc_message_loop, bool create_pipe_now);
+
  private:
   // Called on the plugin thread
   PluginChannel();
@@ -59,6 +73,12 @@ class PluginChannel : public PluginChannelBase {
   // 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.