PPAPI: Introduce concept of ResourceHosts "pinning" each other

ppapi/host/ppapi_host.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 PPAPI_HOST_PPAPI_HOST_H_
 #define PPAPI_HOST_PPAPI_HOST_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 73 matching lines @@
   // ownership of the pointer.
   void AddHostFactoryFilter(scoped_ptr<HostFactory> filter);
 
   // Adds the given message filter to the host. The PpapiHost will take
   // ownership of the pointer.
   void AddInstanceMessageFilter(scoped_ptr<InstanceMessageFilter> filter);
 
   // Returns null if the resource doesn't exist.
   host::ResourceHost* GetResourceHost(PP_Resource resource) const;
 
+  // Pin |owned_host| in memory so long as |owner_host| still needs it. Even
+  // if the plugin is done using |owned_host|, it will be kept alive until
+  // |owner_host| calls UnpinHost.
+  void PinHost(ResourceHost* owner_host, ResourceHost* owned_host);
+  // Called to indicate that the |owner_host| no longer requires |owned_host|.
+  // This may result in |owned_host| being deleted, if:
+  //  (a) The plugin has finished with it, and
+  //  (b) No other ResourceHosts have it pinned.
+  void UnpinHost(ResourceHost* owner_host, ResourceHost* owned_host);
+
  private:
   friend class InstanceMessageFilter;
 
   void HandleResourceCall(
       const proxy::ResourceMessageCallParams& params,
       const IPC::Message& nested_msg,
       HostMessageContext* context);
 
   // Message handlers.
   void OnHostMsgResourceCall(const proxy::ResourceMessageCallParams& params,
                              const IPC::Message& nested_msg);
   void OnHostMsgInProcessResourceCall(
       int routing_id,
       const proxy::ResourceMessageCallParams& params,
       const IPC::Message& nested_msg);
   void OnHostMsgResourceSyncCall(
       const proxy::ResourceMessageCallParams& params,
       const IPC::Message& nested_msg,
       IPC::Message* reply_msg);
   void OnHostMsgResourceCreated(const proxy::ResourceMessageCallParams& param,
                                 PP_Instance instance,
                                 const IPC::Message& nested_msg);
   void OnHostMsgAttachToPendingHost(PP_Resource resource, int pending_host_id);
   void OnHostMsgResourceDestroyed(PP_Resource resource);
 
+  // Get a linked_ptr to the given ResourceHost. It's important to get at the
+  // right one; if we just do:
+  //   linked_ptr<ResourceHost> ptr(raw_host_ptr);
+  // ...we get a linked_ptr with its own separate reference tracking, and we'll
+  // eventually double-delete |*raw_host_ptr|.
+  linked_ptr<ResourceHost> RawToLinkedPtr(ResourceHost* host);
+
   // Non-owning pointer.
   IPC::Sender* sender_;
 
   PpapiPermissions permissions_;
 
   // Filters for resource creation messages. Note that since we don't support
   // deleting these dynamically we don't need to worry about modifications
   // during iteration. If we add that capability, this should be replaced with
   // an ObserverList.
   ScopedVector<HostFactory> host_factory_filters_;
 
   // Filters for instance messages. Note that since we don't support deleting
   // these dynamically we don't need to worry about modifications during
   // iteration. If we add that capability, this should be replaced with an
   // ObserverList.
   ScopedVector<InstanceMessageFilter> instance_message_filters_;
 
   typedef std::map<PP_Resource, linked_ptr<ResourceHost> > ResourceMap;
   ResourceMap resources_;
 
   // Resources that have been created in the host and have not yet had the
   // corresponding PluginResource associated with them.
   // See PpapiHostMsg_AttachToPendingHost.
   typedef std::map<int, linked_ptr<ResourceHost> > PendingHostResourceMap;
   PendingHostResourceMap pending_resource_hosts_;
   int next_pending_resource_host_id_;
 
+  // Some hosts may need to Pin another host in memory for some amount of time.
+  // The main example at the time of writing is PepperGraphics2DHost, which may
+  // have a queue of ImageDataHosts that it requires for doing paints. This
+  // needs to work even if the plugin deletes the ImageDataResource. So
+  // owner_to_owned_map_ keeps a linked_ptr to any "pinned" hosts to make sure
+  // that they live long enough, even when the plugin is done with the resource
+  // and the host gets removed from resource_hosts_ or pending_resource_hosts_.
+  typedef std::map<linked_ptr<ResourceHost>, int > PinCountMap;
+  typedef std::map<ResourceHost*, PinCountMap> OwnerToOwnedHostMap;
+  OwnerToOwnedHostMap owner_to_owned_map_;
+
   DISALLOW_COPY_AND_ASSIGN(PpapiHost);
 };
 
 }  // namespace host
 }  // namespace ppapi
 
 #endif  // PPAPI_HOST_PPAPIE_HOST_H_