Add ChildMessageFilter, a base class for renderer/worker cross-thread MessageFilter

content/child/child_message_filter.cc

+// Copyright 2013 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 "content/child/child_message_filter.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/location.h"
+#include "base/task_runner.h"
+#include "content/child/child_thread.h"
+#include "content/child/thread_safe_sender.h"
+
+namespace content {
+
+class ChildMessageFilter::Internal : public IPC::ChannelProxy::MessageFilter {
+ public:
+  explicit Internal(ChildMessageFilter* filter) : filter_(filter) {}
+
+  virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE {
+    scoped_refptr<base::TaskRunner> runner =
+        filter_->OverrideTaskRunnerForMessage(msg);
+    if (runner && !runner->RunsTasksOnCurrentThread()) {
+      if (!runner->PostTask(
+              FROM_HERE,
+              base::Bind(
+                  base::IgnoreResult(&ChildMessageFilter::OnMessageReceived),
+                  filter_, msg)))
+        filter_->OnStaleMessageReceived(msg);
+      return true;
+    }
+
+    return filter_->OnMessageReceived(msg);
+  }
+
+ private:
+  virtual ~Internal() {}
+  scoped_refptr<ChildMessageFilter> filter_;
+
+  DISALLOW_COPY_AND_ASSIGN(Internal);
+};
+
+bool ChildMessageFilter::Send(IPC::Message* message) {
+  return thread_safe_sender_->Send(message);
+}
+
+base::TaskRunner* ChildMessageFilter::OverrideTaskRunnerForMessage(
+    const IPC::Message& msg) {
+  return NULL;
+}
+
+ChildMessageFilter::ChildMessageFilter()
+    : internal_(NULL),
+      thread_safe_sender_(ChildThread::current()->thread_safe_sender()) {}
+
+ChildMessageFilter::~ChildMessageFilter() {}
+
+IPC::ChannelProxy::MessageFilter* ChildMessageFilter::GetFilter() {
+  if (!internal_)
+    internal_ = new Internal(this);
+  return internal_;
+}
+
+}  // namespace content