Prevent multiple pending UpdatePolicy tasks.

content/renderer/scheduler/deadline_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 "content/renderer/scheduler/deadline_task_runner.h"
+
+#include "base/bind.h"
+
+namespace content {
+
+DeadlineTaskRunner::DeadlineTaskRunner(
+    const base::Closure& callback,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
+    : callback_(callback), task_runner_(task_runner) {
+  cancelable_run_internal_.Reset(
+      base::Bind(&DeadlineTaskRunner::RunInternal, base::Unretained(this)));
+}
+
+DeadlineTaskRunner::~DeadlineTaskRunner() {
+}
+
+void DeadlineTaskRunner::SetDeadline(const tracked_objects::Location& from_here,
+                                     base::TimeDelta delay,
+                                     base::TimeTicks now) {
+  DCHECK(delay > base::TimeDelta());
+  base::TimeTicks deadline = now + delay;
+  if (deadline_.is_null() || deadline < deadline_) {
+    deadline_ = deadline;
+    cancelable_run_internal_.Cancel();
+    task_runner_->PostDelayedTask(from_here,
+                                  cancelable_run_internal_.callback(), delay);
+  }
+}
+
+void DeadlineTaskRunner::RunInternal() {
+  deadline_ = base::TimeTicks();
+  callback_.Run();
+}
+
+}  // namespace content