Revert of Move throttling of background timers into the renderer scheduler

third_party/WebKit/Source/platform/Timer.cpp

Index: third_party/WebKit/Source/platform/Timer.cpp
diff --git a/third_party/WebKit/Source/platform/Timer.cpp b/third_party/WebKit/Source/platform/Timer.cpp
index e27520d7f0a88df31102229e70df637a1ccbab0b..ad619a3cf12d69041cb403d9afafdd874e4e1037 100644
--- a/third_party/WebKit/Source/platform/Timer.cpp
+++ b/third_party/WebKit/Source/platform/Timer.cpp
@@ -43,6 +43,7 @@
 
 TimerBase::TimerBase()
     : m_nextFireTime(0)
+    , m_unalignedNextFireTime(0)
     , m_repeatInterval(0)
     , m_cancellableTimerTask(nullptr)
     , m_webScheduler(Platform::current()->currentThread()->scheduler())
@@ -95,16 +96,23 @@
 {
     ASSERT(m_thread == currentThread());
 
-    double newTime = now + delay;
+    m_unalignedNextFireTime = now + delay;
 
+    double newTime = alignedFireTime(m_unalignedNextFireTime);
     if (m_nextFireTime != newTime) {
         m_nextFireTime = newTime;
         if (m_cancellableTimerTask)
             m_cancellableTimerTask->cancel();
         m_cancellableTimerTask = new CancellableTimerTask(this);
-
-        double delayMs = 1000.0 * (newTime - now);
-        timerTaskRunner()->postDelayedTask(m_location, m_cancellableTimerTask, delayMs);
+        if (newTime != m_unalignedNextFireTime) {
+            // If the timer is being aligned, use postTimerTaskAt() to schedule it
+            // so that the relative order of aligned timers is preserved.
+            // TODO(skyostil): Move timer alignment into the scheduler.
+            m_webScheduler->postTimerTaskAt(m_location, m_cancellableTimerTask, m_nextFireTime);
+        } else {
+            double delayMs = 1000.0 * (newTime - now);
+            m_webScheduler->timerTaskRunner()->postDelayedTask(m_location, m_cancellableTimerTask, delayMs);
+        }
     }
 }
 
@@ -118,24 +126,34 @@
     ASSERT_WITH_MESSAGE(m_thread == currentThread(), "Timer posted by %s %s was run on a different thread", m_location.functionName(), m_location.fileName());
     TRACE_EVENT_SET_SAMPLING_STATE("blink", "BlinkInternal");
 
+    m_nextFireTime = 0;
     if (m_repeatInterval) {
         double now = monotonicallyIncreasingTime();
         // This computation should be drift free, and it will cope if we miss a beat,
         // which can easily happen if the thread is busy.  It will also cope if we get
         // called slightly before m_unalignedNextFireTime, which can happen due to lack
         // of timer precision.
-        double intervalToNextFireTime = m_repeatInterval - fmod(now - m_nextFireTime, m_repeatInterval);
+        double intervalToNextFireTime = m_repeatInterval - fmod(now - m_unalignedNextFireTime, m_repeatInterval);
         setNextFireTime(monotonicallyIncreasingTime(), intervalToNextFireTime);
-    } else {
-        m_nextFireTime = 0;
     }
     fired();
     TRACE_EVENT_SET_SAMPLING_STATE("blink", "Sleeping");
 }
 
+void TimerBase::didChangeAlignmentInterval(double now)
+{
+    setNextFireTime(now, m_unalignedNextFireTime - now);
+}
+
+double TimerBase::nextUnalignedFireInterval() const
+{
+    ASSERT(isActive());
+    return std::max(m_unalignedNextFireTime - monotonicallyIncreasingTime(), 0.0);
+}
+
 bool TimerBase::Comparator::operator()(const TimerBase* a, const TimerBase* b) const
 {
-    return a->m_nextFireTime < b->m_nextFireTime;
+    return a->m_unalignedNextFireTime < b->m_unalignedNextFireTime;
 }
 
 } // namespace blink