Added a ResourceMessageFilter for handling resource messages on another thread.

ppapi/host/background_thread_message_filter.cc

Index: ppapi/host/background_thread_message_filter.cc
diff --git a/ppapi/host/background_thread_message_filter.cc b/ppapi/host/background_thread_message_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..18e436817509b457a70c76777ea8efe3a1e6fc7f
--- /dev/null
+++ b/ppapi/host/background_thread_message_filter.cc
@@ -0,0 +1,102 @@
+// 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.
+
+#include "ppapi/host/background_thread_message_filter.h"
+
+#include "base/task_runner.h"
+#include "content/public/browser/browser_ppapi_host.h"
+#include "ipc/ipc_message.h"
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/host/host_message_context.h"
+#include "ppapi/host/ppapi_host.h"
+#include "ppapi/host/resource_host.h"
+
+namespace ppapi {
+namespace host {
+
+BackgroundThreadMessageFilter::BackgroundThreadMessageFilter()
+    : resource_host_(NULL) {
+}
+
+BackgroundThreadMessageFilter::~BackgroundThreadMessageFilter() {
+}
+
+void BackgroundThreadMessageFilter::OnFilterAdded(ResourceHost* resource_host) {
+  resource_host_ = resource_host;
+}
+
+void BackgroundThreadMessageFilter::OnFilterDestroyed() {
+  resource_host_ = NULL;
+}
+
+bool BackgroundThreadMessageFilter::HandleMessage(
+    const IPC::Message& msg,
+    HostMessageContext* context) {
+  HostMessageContext context_copy = *context;
+
+  content::BrowserThread::ID thread = content::BrowserThread::IO;
+  bool overridden_for_thread = OverrideThreadForMessage(msg, &thread);
+  scoped_refptr<base::TaskRunner> runner =
+      OverrideTaskRunnerForMessage(msg);
+  // The message should not be overridden for both a thread and a task runner.
+  DCHECK(!(overridden_for_thread && runner));
+
+  if (overridden_for_thread) {
+    content::BrowserThread::PostTask(
+        thread, FROM_HERE,
+        base::Bind(&BackgroundThreadMessageFilter::DispatchMessage,
+                   this, msg, context_copy));
+    return true;
+  } else if (runner) {
+    runner->PostTask(FROM_HERE, base::Bind(
+      &BackgroundThreadMessageFilter::DispatchMessage, this, msg,
+      context_copy));
+    return true;
+  }
+
+  return false;
+}
+
+void BackgroundThreadMessageFilter::SendReply(
+    const ReplyMessageContext& context,
+    const IPC::Message& msg) {
+  if (!content::BrowserThread::CurrentlyOn(content::BrowserThread::IO)) {
+    content::BrowserThread::PostTask(content::BrowserThread::IO, FROM_HERE,
+        base::Bind(&BackgroundThreadMessageFilter::SendReply, this, context,
+                   msg));
+  }
+  if (resource_host_)
+    resource_host_->SendReply(context, msg);
+}
+
+void BackgroundThreadMessageFilter::DispatchMessage(
+    const IPC::Message& msg,
+    HostMessageContext context) {
+  RunMessageHandlerAndReply(msg, &context);
+}
+
+bool BackgroundThreadMessageFilter::OverrideThreadForMessage(
+    const IPC::Message& message,
+      content::BrowserThread::ID* thread) {
+  return false;
+}
+
+base::TaskRunner* BackgroundThreadMessageFilter::OverrideTaskRunnerForMessage(
+    const IPC::Message& msg) {
+  return NULL;
+}
+
+RenderViewHostMessageFilter::RenderViewHostMessageFilter(
+    content::BrowserPpapiHost* host,
+    PP_Instance instance) {
+  host->GetRenderViewIDsForInstance(instance, &render_process_id_,
+                                    &render_view_id_);
+}
+
+content::RenderViewHost* RenderViewHostMessageFilter::GetRenderViewHost() {
+  return content::RenderViewHost::FromID(render_process_id_, render_view_id_);
+}
+
+}  // namespace host
+}  // namespace ppapi