[Extensions] Begin making Extension port initialization asynchronous

extensions/renderer/extension_port.h

+// Copyright 2016 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 EXTENSIONS_RENDERER_EXTENSION_PORT_H_
+#define EXTENSIONS_RENDERER_EXTENSION_PORT_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/macros.h"
+
+namespace content {
+class RenderFrame;
+}
+
+namespace extensions {
+
+struct Message;
+class ScriptContext;
+
+// A class to handle sending message port-related IPCs to the browser. Since

[lazyboy, 2016/09/08 00:05:40]

Also point out what this class represents, "info about a specific port" or sth.

[Devlin, 2016/09/08 19:15:30]

Done.

+// global port IDs are assigned asynchronously, this object caches pending
+// messages.
+class ExtensionPort {
+ public:
+  ExtensionPort(ScriptContext* script_context, int local_id);
+  ~ExtensionPort();
+
+  // Sets the global id of the port (that is, the id used in the browser
+  // process to send/receive messages). Any pending messages will be sent.
+  void SetGlobalId(int id);
+
+  // Posts a new message to the port. If the port is not initialized, the
+  // message will be queued until it is.
+  void PostExtensionMessage(std::unique_ptr<Message> message);
+
+  // Closes the port. If there are pending messages, they will still be sent
+  // assuming initialization completes (after which, the port will close).
+  void ClosePort(bool close_channel);

[lazyboy, 2016/09/08 00:05:40]

"Port" prefix seems extraneous given |this| is a ExtensionPort, just Close()
should be enough.

[Devlin, 2016/09/08 19:15:30]

Fair enough, done.

+
+  int local_id() const { return local_id_; }
+  int global_id() const { return global_id_; }
+  bool initialized() const { return global_id_ != -1; }

[lazyboy, 2016/09/08 00:05:40]

IsInitialized() and move definition to cc file.

[Devlin, 2016/09/08 19:15:30]

Why?  This is basically a simple accessor (it doesn't really do any work) - it
just avoids making a bool is_initialized_.  In my mind, CamelCase() functions
are an indication that some significant work is being done (and e.g. you should
cache the result).

[lazyboy, 2016/09/08 21:59:16]

I guess I simplified the meaning of simple accessor, nvm.

+
+ private:
+  // Helper function to send the post message IPC.
+  void PostMessageImpl(content::RenderFrame* render_frame,
+                       const Message& message);
+
+  // Sends the message to the browser that this port has been disconnected.
+  void SendDisconnected(content::RenderFrame* render_frame);
+
+  // The associated ScriptContext for this port. Since these objects are owned
+  // by a NativeHandler, this should always be valid.
+  ScriptContext* script_context_ = nullptr;

[lazyboy, 2016/09/08 00:05:40]

Here and for local_id_: Do you need default member initializer given the
constructor always initializes them?

[Devlin, 2016/09/08 19:15:30]

I think yes, because we want a fallback if the ctor signature changes.  I don't
know if this ever made it into concrete style, but it's an opinion shared by a
few of the folks in the discussion thread:
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/zqB-DySA4V0

"If you use in-class member initialization, then all members that can be value
or default initialized must be." (taken from a post, not style, so not dogma)

[lazyboy, 2016/09/08 21:59:16]

Acknowledged.

+
+  // The local id of the port (used within JS bindings).
+  int local_id_ = -1;
+
+  // The global id of the port (used by the browser process).
+  int global_id_ = -1;
+
+  // The queue of any pending messages to be sent once the port is initialized.
+  std::vector<std::unique_ptr<Message>> pending_messages_;
+
+  // Whether or not the port is disconnected.
+  bool is_disconnected_ = false;
+
+  // Whether to close the full message channel.
+  bool close_channel_ = false;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionPort);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_EXTENSION_PORT_H_