Replace PluginThreadTaskRunner with a simpler MainPluginThreadTaskRunner.

remoting/client/plugin/main_plugin_thread_task_runner.cc

+// Copyright 2015 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/main_plugin_thread_task_runner.h"
+
+#include "base/bind.h"
+#include "ppapi/cpp/core.h"
+
+namespace remoting {
+
+MainPluginThreadTaskRunner::MainPluginThreadTaskRunner()
+    : core_(pp::Module::Get()->core()), callback_factory_(this) {}
+MainPluginThreadTaskRunner::~MainPluginThreadTaskRunner() {}
+
+bool MainPluginThreadTaskRunner::PostDelayedTask(
+    const tracked_objects::Location& from_here,
+    const base::Closure& task,
+    base::TimeDelta delay) {
+  core_->CallOnMainThread(delay.InMilliseconds(),

[Wez, 2015/10/20 23:05:48]

Any risk of e.g. spinning due to this fine-grained to millisecond-grained
conversion?

[Sergey Ulanov, 2015/10/20 23:28:05]

Here CallOnMainThread() is guaranteed to be called once and only once per
PostDelayedTask() call, so there is no possibility of spinning in this class
(like it was before, see the linked bug). But the calling code may still repost
the task if it's called too early. Now I replaced InMilliseconds() with
InMillisecondsRoundedUp() to avoid that problem.

[Wez, 2015/10/20 23:43:52]

Right - spinning callers are as bad as spinning in the task-runner itself!

+                          callback_factory_.NewCallback(
+                              &MainPluginThreadTaskRunner::RunTask, task));
+  return true;
+}
+
+bool MainPluginThreadTaskRunner::PostNonNestableDelayedTask(
+    const tracked_objects::Location& from_here,
+    const base::Closure& task,
+    base::TimeDelta delay) {
+  return PostDelayedTask(from_here, task, delay);
+}
+
+bool MainPluginThreadTaskRunner::RunsTasksOnCurrentThread() const {
+  return core_->IsMainThread();
+}
+
+void MainPluginThreadTaskRunner::RunTask(int32_t result,
+                                         const base::Closure& closure) {
+  closure.Run();
+}
+
+}  // namespace remoting