cc: Add UniqueNotifier to cc/base.

This patch adds a unique notifier, a class that supports scheduling a
callback. It also supports calling additional schedules which
effectively cancel a previous callback and reschedule a new one.

Both version with delayed tasks and immediate tasks are supported.

R=reveman
BUG=none

Review URL: https://codereview.chromium.org/296043005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@273433 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 543 insertions, 0 deletions

diff --git a/cc/base/delayed_unique_notifier.cc b/cc/base/delayed_unique_notifier.cc
new file mode 100644
index 0000000..8086ba6
--- /dev/null
+++ b/cc/base/delayed_unique_notifier.cc
@@ -0,0 +1,74 @@
+// Copyright 2014 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 "cc/base/delayed_unique_notifier.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/location.h"
+#include "base/sequenced_task_runner.h"
+
+namespace cc {
+
+DelayedUniqueNotifier::DelayedUniqueNotifier(
+    base::SequencedTaskRunner* task_runner,
+    const base::Closure& closure,
+    const base::TimeDelta& delay)
+    : task_runner_(task_runner),
+      closure_(closure),
+      delay_(delay),
+      notification_pending_(false),
+      weak_ptr_factory_(this) {
+}
+
+DelayedUniqueNotifier::~DelayedUniqueNotifier() {
+}
+
+void DelayedUniqueNotifier::Schedule() {
+  if (notification_pending_) {
+    next_notification_time_ = Now() + delay_;
+    return;
+  }
+
+  next_notification_time_ = Now() + delay_;
+  task_runner_->PostDelayedTask(FROM_HERE,
+                                base::Bind(&DelayedUniqueNotifier::NotifyIfTime,
+                                           weak_ptr_factory_.GetWeakPtr()),
+                                delay_);
+  notification_pending_ = true;
+}
+
+void DelayedUniqueNotifier::Cancel() {
+  next_notification_time_ = base::TimeTicks();
+}
+
+base::TimeTicks DelayedUniqueNotifier::Now() const {
+  return base::TimeTicks::Now();
+}
+
+void DelayedUniqueNotifier::NotifyIfTime() {
+  // If next notifiaction time is not valid, then this schedule was canceled.
+  if (next_notification_time_.is_null()) {
+    notification_pending_ = false;
+    return;
+  }
+
+  // If the notification was rescheduled or arrived too early for any other
+  // reason, then post another task instead of running the callback.
+  base::TimeTicks now = Now();
+  if (next_notification_time_ > now) {
+    task_runner_->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(&DelayedUniqueNotifier::NotifyIfTime,
+                   weak_ptr_factory_.GetWeakPtr()),
+        next_notification_time_ - now);
+    return;
+  }
+
+  // Note the order here is important since closure might schedule another run.
+  notification_pending_ = false;
+  closure_.Run();
+}
+
+}  // namespace cc
diff --git a/cc/base/delayed_unique_notifier.h b/cc/base/delayed_unique_notifier.h
new file mode 100644
index 0000000..2ae6ae0
--- /dev/null
+++ b/cc/base/delayed_unique_notifier.h
@@ -0,0 +1,58 @@
+// Copyright 2014 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.
+
+#ifndef CC_BASE_DELAYED_UNIQUE_NOTIFIER_H_
+#define CC_BASE_DELAYED_UNIQUE_NOTIFIER_H_
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "cc/base/cc_export.h"
+
+namespace base {
+class SequencedTaskRunner;
+}  // namespace base
+
+namespace cc {
+
+class CC_EXPORT DelayedUniqueNotifier {
+ public:
+  // Configure this notifier to issue the |closure| notification in |delay| time
+  // from Schedule() call.
+  DelayedUniqueNotifier(base::SequencedTaskRunner* task_runner,
+                        const base::Closure& closure,
+                        const base::TimeDelta& delay);
+
+  // Destroying the notifier will ensure that no further notifications will
+  // happen from this class.
+  virtual ~DelayedUniqueNotifier();
+
+  // Schedule a notification to be run. If another notification is already
+  // pending, then it will happen in (at least) given delay from now. That is,
+  // if delay is 16ms and a notification has been scheduled 10ms ago (ie, it
+  // should trigger in no less than 6ms), then calling schedule will ensure that
+  // the only notification that arrives will happen in (at least) 16ms from now.
+  void Schedule();
+
+  // Cancel any previously scheduled runs.
+  void Cancel();
+
+ protected:
+  // Virtual for testing.
+  virtual base::TimeTicks Now() const;
+
+ private:
+  void NotifyIfTime();
+
+  base::SequencedTaskRunner* task_runner_;
+  base::Closure closure_;
+  base::TimeDelta delay_;
+  base::TimeTicks next_notification_time_;
+  bool notification_pending_;
+
+  base::WeakPtrFactory<DelayedUniqueNotifier> weak_ptr_factory_;
+};
+
+}  // namespace cc
+
+#endif  // CC_BASE_DELAYED_UNIQUE_NOTIFIER_H_
diff --git a/cc/base/delayed_unique_notifier_unittest.cc b/cc/base/delayed_unique_notifier_unittest.cc
new file mode 100644
index 0000000..113146a
--- /dev/null
+++ b/cc/base/delayed_unique_notifier_unittest.cc
@@ -0,0 +1,257 @@
+// Copyright 2014 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 <deque>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/test/test_pending_task.h"
+#include "base/test/test_simple_task_runner.h"
+#include "cc/base/delayed_unique_notifier.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+namespace {
+
+class TestNotifier : public DelayedUniqueNotifier {
+ public:
+  TestNotifier(base::SequencedTaskRunner* task_runner,
+               const base::Closure& closure,
+               const base::TimeDelta& delay)
+      : DelayedUniqueNotifier(task_runner, closure, delay) {}
+  virtual ~TestNotifier() {}
+
+  // Overridden from DelayedUniqueNotifier:
+  virtual base::TimeTicks Now() const OVERRIDE { return now_; }
+
+  void SetNow(base::TimeTicks now) { now_ = now; }
+
+ private:
+  base::TimeTicks now_;
+};
+
+class DelayedUniqueNotifierTest : public testing::Test {
+ public:
+  DelayedUniqueNotifierTest() : notification_count_(0) {}
+
+  virtual void SetUp() OVERRIDE {
+    notification_count_ = 0;
+    task_runner_ = make_scoped_refptr(new base::TestSimpleTaskRunner);
+  }
+
+  void Notify() { ++notification_count_; }
+
+  int NotificationCount() const { return notification_count_; }
+
+  std::deque<base::TestPendingTask> TakePendingTasks() {
+    std::deque<base::TestPendingTask> tasks = task_runner_->GetPendingTasks();
+    task_runner_->ClearPendingTasks();
+    return tasks;
+  }
+
+ protected:
+  int notification_count_;
+  scoped_refptr<base::TestSimpleTaskRunner> task_runner_;
+};
+
+TEST_F(DelayedUniqueNotifierTest, ZeroDelay) {
+  base::TimeDelta delay = base::TimeDelta::FromInternalValue(0);
+  TestNotifier notifier(
+      task_runner_,
+      base::Bind(&DelayedUniqueNotifierTest::Notify, base::Unretained(this)),
+      delay);
+
+  EXPECT_EQ(0, NotificationCount());
+
+  // Basic schedule for |delay| from now.
+  base::TimeTicks schedule_time =
+      base::TimeTicks() + base::TimeDelta::FromInternalValue(10);
+
+  notifier.SetNow(schedule_time);
+  notifier.Schedule();
+
+  std::deque<base::TestPendingTask> tasks = TakePendingTasks();
+  ASSERT_EQ(1u, tasks.size());
+  EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+  tasks[0].task.Run();
+  EXPECT_EQ(1, NotificationCount());
+
+  // 5 schedules should result in only one run.
+  for (int i = 0; i < 5; ++i)
+    notifier.Schedule();
+
+  tasks = TakePendingTasks();
+  ASSERT_EQ(1u, tasks.size());
+  EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+  tasks[0].task.Run();
+  EXPECT_EQ(2, NotificationCount());
+}
+
+TEST_F(DelayedUniqueNotifierTest, SmallDelay) {
+  base::TimeDelta delay = base::TimeDelta::FromInternalValue(20);
+  TestNotifier notifier(
+      task_runner_,
+      base::Bind(&DelayedUniqueNotifierTest::Notify, base::Unretained(this)),
+      delay);
+
+  EXPECT_EQ(0, NotificationCount());
+
+  // Basic schedule for |delay| from now (now: 30, run time: 50).
+  base::TimeTicks schedule_time =
+      base::TimeTicks() + base::TimeDelta::FromInternalValue(30);
+
+  notifier.SetNow(schedule_time);
+  notifier.Schedule();
+
+  std::deque<base::TestPendingTask> tasks = TakePendingTasks();
+
+  ASSERT_EQ(1u, tasks.size());
+  EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+  // It's not yet time to run, so we expect no notifications.
+  tasks[0].task.Run();
+  EXPECT_EQ(0, NotificationCount());
+
+  tasks = TakePendingTasks();
+
+  ASSERT_EQ(1u, tasks.size());
+  // Now the time should be delay minus whatever the value of now happens to be
+  // (now: 30, run time: 50).
+  base::TimeTicks scheduled_run_time = notifier.Now() + delay;
+  base::TimeTicks scheduled_delay =
+      base::TimeTicks() + (scheduled_run_time - notifier.Now());
+  EXPECT_EQ(scheduled_delay, tasks[0].GetTimeToRun());
+
+  // Move closer to the run time (time: 49, run time: 50).
+  notifier.SetNow(notifier.Now() + base::TimeDelta::FromInternalValue(19));
+
+  // It's not yet time to run, so we expect no notifications.
+  tasks[0].task.Run();
+  EXPECT_EQ(0, NotificationCount());
+
+  tasks = TakePendingTasks();
+  ASSERT_EQ(1u, tasks.size());
+
+  // Now the time should be delay minus whatever the value of now happens to be.
+  scheduled_delay = base::TimeTicks() + (scheduled_run_time - notifier.Now());
+  EXPECT_EQ(scheduled_delay, tasks[0].GetTimeToRun());
+
+  // Move to exactly the run time (time: 50, run time: 50).
+  notifier.SetNow(notifier.Now() + base::TimeDelta::FromInternalValue(1));
+
+  // It's time to run!
+  tasks[0].task.Run();
+  EXPECT_EQ(1, NotificationCount());
+
+  tasks = TakePendingTasks();
+  EXPECT_EQ(0u, tasks.size());
+}
+
+TEST_F(DelayedUniqueNotifierTest, RescheduleDelay) {
+  base::TimeDelta delay = base::TimeDelta::FromInternalValue(20);
+  TestNotifier notifier(
+      task_runner_,
+      base::Bind(&DelayedUniqueNotifierTest::Notify, base::Unretained(this)),
+      delay);
+
+  base::TimeTicks schedule_time;
+  // Move time 19 units forward and reschedule, expecting that we still need to
+  // run in |delay| time and we don't get a notification.
+  for (int i = 0; i < 10; ++i) {
+    EXPECT_EQ(0, NotificationCount());
+
+    // Move time forward 19 units.
+    schedule_time = notifier.Now() + base::TimeDelta::FromInternalValue(19);
+    notifier.SetNow(schedule_time);
+    notifier.Schedule();
+
+    std::deque<base::TestPendingTask> tasks = TakePendingTasks();
+
+    ASSERT_EQ(1u, tasks.size());
+    EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+    // It's not yet time to run, so we expect no notifications.
+    tasks[0].task.Run();
+    EXPECT_EQ(0, NotificationCount());
+  }
+
+  // Move time forward 20 units, expecting a notification.
+  schedule_time = notifier.Now() + base::TimeDelta::FromInternalValue(20);
+  notifier.SetNow(schedule_time);
+
+  std::deque<base::TestPendingTask> tasks = TakePendingTasks();
+
+  ASSERT_EQ(1u, tasks.size());
+  EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+  // Time to run!
+  tasks[0].task.Run();
+  EXPECT_EQ(1, NotificationCount());
+}
+
+TEST_F(DelayedUniqueNotifierTest, Cancel) {
+  base::TimeDelta delay = base::TimeDelta::FromInternalValue(20);
+  TestNotifier notifier(
+      task_runner_,
+      base::Bind(&DelayedUniqueNotifierTest::Notify, base::Unretained(this)),
+      delay);
+
+  EXPECT_EQ(0, NotificationCount());
+
+  // Schedule for |delay| seconds from now.
+  base::TimeTicks schedule_time =
+      notifier.Now() + base::TimeDelta::FromInternalValue(10);
+  notifier.SetNow(schedule_time);
+  notifier.Schedule();
+
+  // Cancel the run.
+  notifier.Cancel();
+
+  std::deque<base::TestPendingTask> tasks = TakePendingTasks();
+
+  ASSERT_EQ(1u, tasks.size());
+  EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+  // Time to run, but a canceled task!
+  tasks[0].task.Run();
+  EXPECT_EQ(0, NotificationCount());
+
+  tasks = TakePendingTasks();
+  EXPECT_EQ(0u, tasks.size());
+
+  notifier.Schedule();
+  tasks = TakePendingTasks();
+
+  ASSERT_EQ(1u, tasks.size());
+  EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+  // Advance the time.
+  notifier.SetNow(notifier.Now() + delay);
+
+  // This should run since it wasn't scheduled.
+  tasks[0].task.Run();
+  EXPECT_EQ(1, NotificationCount());
+
+  for (int i = 0; i < 10; ++i)
+    notifier.Schedule();
+
+  notifier.Cancel();
+  tasks = TakePendingTasks();
+
+  ASSERT_EQ(1u, tasks.size());
+  EXPECT_EQ(base::TimeTicks() + delay, tasks[0].GetTimeToRun());
+
+  // Time to run, but a canceled task!
+  notifier.SetNow(notifier.Now() + delay);
+  tasks[0].task.Run();
+  EXPECT_EQ(1, NotificationCount());
+
+  tasks = TakePendingTasks();
+  EXPECT_EQ(0u, tasks.size());
+}
+
+}  // namespace
+}  // namespace cc
diff --git a/cc/base/unique_notifier.cc b/cc/base/unique_notifier.cc
new file mode 100644
index 0000000..0656c6d
--- /dev/null
+++ b/cc/base/unique_notifier.cc
@@ -0,0 +1,42 @@
+// Copyright 2014 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 "cc/base/unique_notifier.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/location.h"
+#include "base/sequenced_task_runner.h"
+
+namespace cc {
+
+UniqueNotifier::UniqueNotifier(base::SequencedTaskRunner* task_runner,
+                               const base::Closure& closure)
+    : task_runner_(task_runner),
+      closure_(closure),
+      notification_pending_(false),
+      weak_ptr_factory_(this) {
+}
+
+UniqueNotifier::~UniqueNotifier() {
+}
+
+void UniqueNotifier::Schedule() {
+  if (notification_pending_)
+    return;
+
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&UniqueNotifier::Notify, weak_ptr_factory_.GetWeakPtr()));
+  notification_pending_ = true;
+}
+
+void UniqueNotifier::Notify() {
+  // Note that the order here is important in case closure schedules another
+  // run.
+  notification_pending_ = false;
+  closure_.Run();
+}
+
+}  // namespace cc
diff --git a/cc/base/unique_notifier.h b/cc/base/unique_notifier.h
new file mode 100644
index 0000000..4752f6f
--- /dev/null
+++ b/cc/base/unique_notifier.h
@@ -0,0 +1,44 @@
+// Copyright 2014 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.
+
+#ifndef CC_BASE_UNIQUE_NOTIFIER_H_
+#define CC_BASE_UNIQUE_NOTIFIER_H_
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "cc/base/cc_export.h"
+
+namespace base {
+class SequencedTaskRunner;
+}  // namespace base
+
+namespace cc {
+
+class CC_EXPORT UniqueNotifier {
+ public:
+  // Configure this notifier to issue the |closure| notification when scheduled.
+  UniqueNotifier(base::SequencedTaskRunner* task_runner,
+                 const base::Closure& closure);
+
+  // Destroying the notifier will ensure that no further notifications will
+  // happen from this class.
+  ~UniqueNotifier();
+
+  // Schedule a notification to be run. If another notification is already
+  // pending, then only one notification will take place.
+  void Schedule();
+
+ private:
+  void Notify();
+
+  base::SequencedTaskRunner* task_runner_;
+  base::Closure closure_;
+  bool notification_pending_;
+
+  base::WeakPtrFactory<UniqueNotifier> weak_ptr_factory_;
+};
+
+}  // namespace cc
+
+#endif  // CC_BASE_UNIQUE_NOTIFIER_H_
diff --git a/cc/base/unique_notifier_unittest.cc b/cc/base/unique_notifier_unittest.cc
new file mode 100644
index 0000000..8c7b0d1
--- /dev/null
+++ b/cc/base/unique_notifier_unittest.cc
@@ -0,0 +1,62 @@
+// Copyright 2014 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 "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/run_loop.h"
+#include "base/single_thread_task_runner.h"
+#include "cc/base/unique_notifier.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+namespace {
+
+class UniqueNotifierTest : public testing::Test {
+ public:
+  UniqueNotifierTest() : notification_count_(0) {}
+
+  virtual void SetUp() OVERRIDE { ResetNotificationCount(); }
+
+  void Notify() { ++notification_count_; }
+
+  int NotificationCount() const { return notification_count_; }
+
+  void ResetNotificationCount() { notification_count_ = 0; }
+
+ protected:
+  int notification_count_;
+};
+
+TEST_F(UniqueNotifierTest, Schedule) {
+  {
+    UniqueNotifier notifier(
+        base::MessageLoopProxy::current(),
+        base::Bind(&UniqueNotifierTest::Notify, base::Unretained(this)));
+
+    EXPECT_EQ(0, NotificationCount());
+
+    // Basic schedule should result in a run.
+    notifier.Schedule();
+
+    base::RunLoop().RunUntilIdle();
+    EXPECT_EQ(1, NotificationCount());
+
+    // Multiple schedules should only result in one run.
+    for (int i = 0; i < 5; ++i)
+      notifier.Schedule();
+
+    base::RunLoop().RunUntilIdle();
+    EXPECT_EQ(2, NotificationCount());
+
+    notifier.Schedule();
+  }
+
+  // Notifier went out of scope, so we don't expect to get a notification.
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(2, NotificationCount());
+}
+
+}  // namespace
+}  // namespace cc
diff --git a/cc/cc.gyp b/cc/cc.gyp
index d05de57..2539323b 100644
--- a/cc/cc.gyp
+++ b/cc/cc.gyp
@@ -64,6 +64,8 @@
         'animation/transform_operations.cc',
         'animation/transform_operations.h',
         'base/completion_event.h',
+        'base/delayed_unique_notifier.cc',
+        'base/delayed_unique_notifier.h',
         'base/invalidation_region.cc',
         'base/invalidation_region.h',
         'base/latency_info_swap_promise.cc',
@@ -87,6 +89,8 @@
         'base/switches.h',
         'base/tiling_data.cc',
         'base/tiling_data.h',
+        'base/unique_notifier.cc',
+        'base/unique_notifier.h',
         'base/util.h',
         'debug/benchmark_instrumentation.cc',
         'debug/benchmark_instrumentation.h',
diff --git a/cc/cc_tests.gyp b/cc/cc_tests.gyp
index 857d098..119403a 100644
--- a/cc/cc_tests.gyp
+++ b/cc/cc_tests.gyp
@@ -13,12 +13,14 @@
       'animation/scrollbar_animation_controller_linear_fade_unittest.cc',
       'animation/scrollbar_animation_controller_thinning_unittest.cc',
       'animation/transform_operations_unittest.cc',
+      'base/delayed_unique_notifier_unittest.cc',
       'base/float_quad_unittest.cc',
       'base/math_util_unittest.cc',
       'base/region_unittest.cc',
       'base/rolling_time_delta_history_unittest.cc',
       'base/scoped_ptr_vector_unittest.cc',
       'base/tiling_data_unittest.cc',
+      'base/unique_notifier_unittest.cc',
       'base/util_unittest.cc',
       'debug/micro_benchmark_controller_unittest.cc',
       'input/top_controls_manager_unittest.cc',