Reapply r51857 to start building chromoting plugin. Update for ppapi changes.

remoting/client/plugin/pepper_util.cc

+// Copyright (c) 2010 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 "remoting/client/plugin/pepper_util.h"
+
+#include "base/task.h"
+#include "third_party/ppapi/c/pp_completion_callback.h"
+#include "third_party/ppapi/cpp/module.h"
+
+namespace remoting {
+
+void CompletionCallbackTaskAdapter(void* user_data, int32_t not_used) {
+  Task* task = reinterpret_cast<Task*>(user_data);
+  task->Run();
+  delete task;
+}
+
+pp::CompletionCallback TaskToCompletionCallback(Task* task) {
+  return pp::CompletionCallback(&CompletionCallbackTaskAdapter, task);
+}
+
+void RunTaskOnPluginThread(Task* task) {
+  pp::Module::Get()->core()->CallOnMainThread(
+      0 /* run immediately */,
+      TaskToCompletionCallback(task),
+      0 /* unused value */
+      );
+}
+
+}  // namespace remoting