Add ability to create pending resource hosts.

ppapi/proxy/ppapi_messages.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.
 
 // Multiply-included message header, no traditional include guard.
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
@@ skipping 1397 matching lines @@
 // message will be resource-type-specific.
 IPC_MESSAGE_CONTROL3(PpapiHostMsg_ResourceCreated,
                      ppapi::proxy::ResourceMessageCallParams /* call_params */,
                      PP_Instance  /* instance */,
                      IPC::Message /* nested_msg */)
 
 // Notification that a resource has been destroyed in the plugin.
 IPC_MESSAGE_CONTROL1(PpapiHostMsg_ResourceDestroyed,
                      PP_Resource /* resource */)
 
+// Most resources are created by the plugin, which then sends a ResourceCreated
+// message to create a corresponding ResourceHost in the renderer or browser
+// host process. However, some resources are first created in the host and
+// "pushed" or returned to the plugin.
+//
+// In this case, the host will create a "pending" ResourceHost object which
+// is identified by an ID. The ID is sent to the plugin process and the
+// PluginResource object is created. This message is sent from the plugin to
+// the host process to connect the PluginResource and the pending ResourceHost
+// (at which point, it's no longer pending).
+IPC_MESSAGE_CONTROL2(PpapiHostMsg_AttachToPendingHost,
+                     PP_Resource /* resource */,
+                     int /* pending_host_id */)
+
 // A resource call is a request from the plugin to the host. It may or may not
 // require a reply, depending on the params. The nested message will be
 // resource-type-specific.
 IPC_MESSAGE_CONTROL2(PpapiHostMsg_ResourceCall,
                      ppapi::proxy::ResourceMessageCallParams /* call_params */,
                      IPC::Message /* nested_msg */)
 
 // A resource reply is a response to a ResourceCall from a host to the
 // plugin. The resource ID + sequence number in the params will correspond to
 // that of the previous ResourceCall.
@@ skipping 256 matching lines @@
                      std::vector<ppapi::HostResource> /* buffers */,
                      uint32_t /* buffer_size */)
 IPC_MESSAGE_CONTROL1(PpapiPluginMsg_VideoCapture_OnStatus,
                      uint32_t /* status */)
 IPC_MESSAGE_CONTROL1(PpapiPluginMsg_VideoCapture_OnError,
                      uint32_t /* error */)
 IPC_MESSAGE_CONTROL1(PpapiPluginMsg_VideoCapture_OnBufferReady,
                      uint32_t /* buffer */)
 
 #endif  // !defined(OS_NACL) && !defined(NACL_WIN64)