Add support for external out-of-process PPAPI plugins in the browser.

content/browser/renderer_host/pepper/browser_ppapi_host_impl.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_BROWSER_RENDERER_HOST_PEPPER_BROWSER_PPAPI_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_PEPPER_BROWSER_PPAPI_HOST_IMPL_H_
 
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "content/browser/renderer_host/pepper/content_browser_pepper_host_factory.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/browser_ppapi_host.h"
 #include "ipc/ipc_channel_proxy.h"
 #include "ppapi/host/ppapi_host.h"
 
-namespace IPC {
-class Sender;
-}
-
 namespace content {
 
-class CONTENT_EXPORT BrowserPpapiHostImpl
-    : public BrowserPpapiHost,
-      public IPC::ChannelProxy::MessageFilter {
+class CONTENT_EXPORT BrowserPpapiHostImpl : public BrowserPpapiHost {
  public:
   // The creator is responsible for calling set_plugin_process_handle as soon
   // as it is known (we start the process asynchronously so it won't be known
   // when this object is created).
   BrowserPpapiHostImpl(IPC::Sender* sender,
                        const ppapi::PpapiPermissions& permissions);
-
-  // IPC::ChannelProxy::MessageFilter.
-  virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
+  virtual ~BrowserPpapiHostImpl();
 
   // BrowserPpapiHost.
   virtual ppapi::host::PpapiHost* GetPpapiHost() OVERRIDE;
   virtual base::ProcessHandle GetPluginProcessHandle() const OVERRIDE;
   virtual bool IsValidInstance(PP_Instance instance) const OVERRIDE;
   virtual bool GetRenderViewIDsForInstance(PP_Instance instance,
                                            int* render_process_id,
                                            int* render_view_id) const OVERRIDE;
 
   void set_plugin_process_handle(base::ProcessHandle handle) {
     plugin_process_handle_ = handle;
   }
 
   // These two functions are notifications that an instance has been created
   // or destroyed. They allow us to maintain a mapping of PP_Instance to view
   // IDs in the browser process.
   void AddInstanceForView(PP_Instance instance,
                           int render_process_id,
                           int render_view_id);
   void DeleteInstanceForView(PP_Instance instance);
 
+  scoped_refptr<IPC::ChannelProxy::MessageFilter> message_filter() {
+    return message_filter_;
+  }
+
  private:
   friend class BrowserPpapiHostTest;
 
   struct RenderViewIDs {
     int process_id;
     int view_id;
   };
   typedef std::map<PP_Instance, RenderViewIDs> InstanceToViewMap;
 
-  virtual ~BrowserPpapiHostImpl();
+  // Implementing MessageFilter on BrowserPpapiHostImpl makes it ref-counted,
+  // preventing us from returning these to embedders without holding a
+  // reference. To avoid that, define a message filter object.
+  class HostMessageFilter : public IPC::ChannelProxy::MessageFilter {
+   public:
+    explicit HostMessageFilter(ppapi::host::PpapiHost* ppapi_host)
+        : ppapi_host_(ppapi_host) {}
+    // IPC::ChannelProxy::MessageFilter.
+    virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
+
+   private:
+    virtual ~HostMessageFilter() {}
+
+    ppapi::host::PpapiHost* ppapi_host_;

[brettw, 2012/11/07 00:18:11]

You should have a way for this back pointer to be nulled out and do this in the
BrowserPpapiHost destructor. This filter may outlive your class, so you should
always check the pointer nullness before dispatching.

[bbudge, 2012/11/07 00:51:46]

Good catch. Done.

+  };
 
   ppapi::host::PpapiHost ppapi_host_;
   base::ProcessHandle plugin_process_handle_;
 
   // Tracks all PP_Instances in this plugin and maps them to
   // RenderProcess/RenderView IDs.
   InstanceToViewMap instance_to_view_;
 
+  scoped_refptr<HostMessageFilter> message_filter_;
+
   DISALLOW_COPY_AND_ASSIGN(BrowserPpapiHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_PEPPER_BROWSER_PPAPI_HOST_IMPL_H_