Adds a flag to support "Virtual Time" to the blink scheduler

components/scheduler/child/virtual_time_tqm_delegate.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 "components/scheduler/child/virtual_time_tqm_delegate.h"
+
+namespace scheduler {
+
+// static
+scoped_refptr<VirtualTimeTqmDelegate> VirtualTimeTqmDelegate::Create(
+    base::MessageLoop* message_loop,
+    base::TimeTicks initial_now) {
+  return make_scoped_refptr(
+      new VirtualTimeTqmDelegate(message_loop, initial_now));
+}
+
+VirtualTimeTqmDelegate::VirtualTimeTqmDelegate(base::MessageLoop* message_loop,
+                                               base::TimeTicks initial_now)
+    : message_loop_(message_loop),
+      message_loop_task_runner_(message_loop->task_runner()),
+      now_(initial_now) {}
+
+VirtualTimeTqmDelegate::~VirtualTimeTqmDelegate() {
+  RestoreDefaultTaskRunner();
+}
+
+void VirtualTimeTqmDelegate::SetDefaultTaskRunner(
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
+  message_loop_->SetTaskRunner(task_runner);
+}
+
+void VirtualTimeTqmDelegate::RestoreDefaultTaskRunner() {
+  if (base::MessageLoop::current() == message_loop_)
+    message_loop_->SetTaskRunner(message_loop_task_runner_);
+}
+
+bool VirtualTimeTqmDelegate::PostDelayedTask(
+    const tracked_objects::Location& from_here,
+    const base::Closure& task,
+    base::TimeDelta delay) {
+  if (delay > base::TimeDelta()) {
+    base::TimeTicks fire_time = now_ + delay;
+    delayed_wakeup_multimap_.insert(std::make_pair(fire_time, task));
+  }
+  return message_loop_task_runner_->PostDelayedTask(from_here, task, delay);
+}
+
+bool VirtualTimeTqmDelegate::PostNonNestableDelayedTask(
+    const tracked_objects::Location& from_here,
+    const base::Closure& task,
+    base::TimeDelta delay) {
+  return message_loop_task_runner_->PostNonNestableDelayedTask(from_here, task,
+                                                               delay);
+}
+
+bool VirtualTimeTqmDelegate::RunsTasksOnCurrentThread() const {
+  return message_loop_task_runner_->RunsTasksOnCurrentThread();
+}
+
+bool VirtualTimeTqmDelegate::IsNested() const {
+  return message_loop_->IsNested();
+}
+
+base::TimeTicks VirtualTimeTqmDelegate::NowTicks() {
+  return now_;
+}
+
+void VirtualTimeTqmDelegate::AdvancedTimeTo(base::TimeTicks now) {
+  now_ = now;
+  DCHECK_GE(now, now_);
+  while (!delayed_wakeup_multimap_.empty()) {
+    DelayedWakeupMultimap::iterator next_wakeup =
+        delayed_wakeup_multimap_.begin();
+    if (next_wakeup->first > now)
+      break;
+    message_loop_task_runner_->PostDelayedTask(FROM_HERE, next_wakeup->second,
+                                               base::TimeDelta());
+    delayed_wakeup_multimap_.erase(next_wakeup);
+  }
+}
+
+void VirtualTimeTqmDelegate::OnNoMoreImmediateWork() {
+  if (delayed_wakeup_multimap_.empty())
+    return;
+
+  AdvancedTimeTo(delayed_wakeup_multimap_.begin()->first);
+}
+
+}  // namespace scheduler