Revert 210101 "cc: Fix and simplify DelayBasedTimeSource"

cc/scheduler/delay_based_time_source_unittest.cc

 // Copyright 2011 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/scheduler/delay_based_time_source.h"
 
 #include "base/basictypes.h"
 #include "base/test/test_simple_task_runner.h"
 #include "cc/test/scheduler_test_common.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 70 matching lines @@
 // At 60Hz, when the tick returns at exactly the requested next time, make sure
 // a 16ms next delay is posted.
 TEST(DelayBasedTimeSource, NextDelaySaneWhenExactlyOnRequestedTime) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   timer->SetNow(timer->Now() + Interval());
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 }
 
 // At 60Hz, when the tick returns at slightly after the requested next time,
 // make sure a 16ms next delay is posted.
 TEST(DelayBasedTimeSource, NextDelaySaneWhenSlightlyAfterRequestedTime) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   timer->SetNow(timer->Now() + Interval() +
                 base::TimeDelta::FromMicroseconds(1));
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 }
 
 // At 60Hz, when the tick returns at exactly 2*interval after the requested next
-// time, make sure a 0ms next delay is posted.
+// time, make sure a 16ms next delay is posted.
 TEST(DelayBasedTimeSource, NextDelaySaneWhenExactlyTwiceAfterRequestedTime) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   timer->SetNow(timer->Now() + 2 * Interval());
   task_runner->RunPendingTasks();
 
-  EXPECT_EQ(0, task_runner->NextPendingTaskDelay().InMilliseconds());
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 }
 
 // At 60Hz, when the tick returns at 2*interval and a bit after the requested
 // next time, make sure a 16ms next delay is posted.
 TEST(DelayBasedTimeSource, NextDelaySaneWhenSlightlyAfterTwiceRequestedTime) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   timer->SetNow(timer->Now() + 2 * Interval() +
                 base::TimeDelta::FromMicroseconds(1));
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 }
 
 // At 60Hz, when the tick returns halfway to the next frame time, make sure
 // a correct next delay value is posted.
 TEST(DelayBasedTimeSource, NextDelaySaneWhenHalfAfterRequestedTime) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   timer->SetNow(timer->Now() + Interval() +
                 base::TimeDelta::FromMilliseconds(8));
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(8, task_runner->NextPendingTaskDelay().InMilliseconds());
 }
 
 // If the timebase and interval are updated with a jittery source, we want to
 // make sure we do not double tick.
 TEST(DelayBasedTimeSource, SaneHandlingOfJitteryTimebase) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   // Jitter timebase ~1ms late
   timer->SetNow(timer->Now() + Interval());
   timer->SetTimebaseAndInterval(
       timer->Now() + base::TimeDelta::FromMilliseconds(1), Interval());
   task_runner->RunPendingTasks();
 
@@ skipping 10 matching lines @@
 }
 
 TEST(DelayBasedTimeSource, HandlesSignificantTimebaseChangesImmediately) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   // Tick, then shift timebase by +7ms.
   timer->SetNow(timer->Now() + Interval());
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
@@ skipping 23 matching lines @@
 }
 
 TEST(DelayBasedTimeSource, HanldlesSignificantIntervalChangesImmediately) {
   scoped_refptr<base::TestSimpleTaskRunner> task_runner =
       new base::TestSimpleTaskRunner;
   FakeTimeSourceClient client;
   scoped_refptr<FakeDelayBasedTimeSource> timer =
       FakeDelayBasedTimeSource::Create(Interval(), task_runner.get());
   timer->SetClient(&client);
   timer->SetActive(true);
-  // Run the first tick.
+  // Run the first task, as that activates the timer and picks up a timebase.
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
   // Tick, then double the interval.
   timer->SetNow(timer->Now() + Interval());
   task_runner->RunPendingTasks();
 
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 
@@ skipping 107 matching lines @@
 
   // Start the timer again, but before the next tick time the timer previously
   // planned on using. That same tick time should still be targeted.
   timer->SetNow(timer->Now() + base::TimeDelta::FromMilliseconds(20));
   timer->SetActive(true);
   EXPECT_EQ(13, task_runner->NextPendingTaskDelay().InMilliseconds());
 }
 
 }  // namespace
 }  // namespace cc