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

content/browser/renderer_host/pepper/browser_ppapi_host_impl.h

Index: content/browser/renderer_host/pepper/browser_ppapi_host_impl.h
===================================================================
--- content/browser/renderer_host/pepper/browser_ppapi_host_impl.h	(revision 166155)
+++ content/browser/renderer_host/pepper/browser_ppapi_host_impl.h	(working copy)
@@ -15,25 +15,17 @@
 #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);
+  virtual ~BrowserPpapiHostImpl();
 
-  // IPC::ChannelProxy::MessageFilter.
-  virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
-
   // BrowserPpapiHost.
   virtual ppapi::host::PpapiHost* GetPpapiHost() OVERRIDE;
   virtual base::ProcessHandle GetPluginProcessHandle() const OVERRIDE;
@@ -54,6 +46,10 @@
                           int render_view_id);
   void DeleteInstanceForView(PP_Instance instance);
 
+  scoped_refptr<IPC::ChannelProxy::MessageFilter> message_filter() {
+    return message_filter_;
+  }
+
  private:
   friend class BrowserPpapiHostTest;
 
@@ -63,8 +59,22 @@
   };
   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_;
 
@@ -72,6 +82,8 @@
   // RenderProcess/RenderView IDs.
   InstanceToViewMap instance_to_view_;
 
+  scoped_refptr<HostMessageFilter> message_filter_;
+
   DISALLOW_COPY_AND_ASSIGN(BrowserPpapiHostImpl);
 };