Browser Plugin: Implement BrowserPluginObserver.

content/public/renderer/browser_plugin/browser_plugin_observer.h

+// 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.
+
+#ifndef CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_OBSERVER_H_
+#define CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_OBSERVER_H_
+
+#include "base/compiler_specific.h"
+#include "content/common/content_export.h"
+#include "ipc/ipc_listener.h"
+#include "ipc/ipc_sender.h"
+
+namespace content {
+
+class BrowserPlugin;
+class BrowserPluginImpl;
+
+class CONTENT_EXPORT BrowserPluginObserver : public IPC::Listener,

[sadrul, 2013/01/09 15:21:54]

It looks like a BPO can be an observer for a single browser-plugin at a time? I
think in chromium code, some kind of observers can observe any number of items
(aura::WindowObserver), while some observers can observer only a single item at
a time (content::RenderViewObserver). So this is OK (although I prefer the
former version of observers). But please add doc.

[Fady Samuel, 2013/01/09 17:41:24]

Done.

+                                             public IPC::Sender {
+ public:
+  // By default, observers will be deleted when the BrowserPlugin goes away.  If
+  // they want to outlive it, they can override this function.
+  virtual void OnDestruct();
+
+  // IPC::Listener implementation.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+
+ protected:
+  explicit BrowserPluginObserver(BrowserPlugin* browser_plugin);
+  virtual ~BrowserPluginObserver();
+
+  // IPC::Sender implementation.
+  virtual bool Send(IPC::Message* message) OVERRIDE;
+
+  BrowserPlugin* browser_plugin() const;
+  int instance_id() { return instance_id_; }

[sadrul, 2013/01/09 15:21:54]

const this too?

[Fady Samuel, 2013/01/09 17:41:24]

Done.

+
+ private:
+  friend class BrowserPluginImpl;
+
+  // This is called by the BrowserPlugin when it's going away so that this
+  // object can null out its pointer.
+  void BrowserPluginGone();
+
+  BrowserPlugin* browser_plugin_;
+  // The instance ID of the associated BrowserPlugin.
+  int instance_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserPluginObserver);
+

[sadrul, 2013/01/09 15:21:54]

remove blank line

[Fady Samuel, 2013/01/09 17:41:24]

Done.

+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_OBSERVER_H_