cc: Handle future timebases properly in 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 287 matching lines @@
 
   client.Reset();
   task_runner->ClearPendingTasks();
   task_runner->RunPendingTasks();
   timer->SetTimebaseAndInterval(base::TimeTicks() + Interval() * 3, Interval());
 
   EXPECT_FALSE(client.TickCalled());  // Make sure pending tasks were canceled.
   EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
 }
 
+TEST(DelayBasedTimeSource, JitteryRuntimeWithFutureTimebases) {
+  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.
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  base::TimeTicks future_timebase = timer->Now() + Interval() * 10;
+
+  // 1ms jitter
+  base::TimeDelta jitter1 = base::TimeDelta::FromMilliseconds(1);
+
+  // Tick with +1ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() + jitter1);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(15, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with 0ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() - jitter1);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with -1ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() - jitter1);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(17, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with 0ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() + jitter1);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // 8 ms jitter
+  base::TimeDelta jitter8 = base::TimeDelta::FromMilliseconds(8);
+
+  // Tick with +8ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() + jitter8);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(8, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with 0ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() - jitter8);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with -8ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() - jitter8);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(24, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with 0ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() + jitter8);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // 15 ms jitter
+  base::TimeDelta jitter15  = base::TimeDelta::FromMilliseconds(15);
+
+  // Tick with +15ms jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() + jitter15);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(1, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with 0ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() - jitter15);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with -15ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() - jitter15);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(31, task_runner->NextPendingTaskDelay().InMilliseconds());
+
+  // Tick with 0ms of jitter
+  future_timebase += Interval();
+  timer->SetTimebaseAndInterval(future_timebase, Interval());
+  timer->SetNow(timer->Now() + Interval() + jitter15);
+  task_runner->RunPendingTasks();
+  EXPECT_EQ(16, task_runner->NextPendingTaskDelay().InMilliseconds());
+}
+
 TEST(DelayBasedTimeSourceTest, AchievesTargetRateWithNoNoise) {
   int num_iterations = 10;
 
   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);
@@ skipping 74 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