[blink] Support moving timers between WebTaskRunners

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 b02e8b6c8e52b447cd9e6b50c130d73445ec50f8..022329002b560e085d494d7aeac285143bd3dd1d 100644
--- a/third_party/WebKit/Source/platform/Timer.cpp
+++ b/third_party/WebKit/Source/platform/Timer.cpp
@@ -85,6 +85,24 @@ double TimerBase::nextFireInterval() const {
   return m_nextFireTime - current;
 }
 
+void TimerBase::moveToNewTaskRunner(WebTaskRunner* taskRunner) {
+#if DCHECK_IS_ON()
+  DCHECK_EQ(m_thread, currentThread());
+  DCHECK(taskRunner->runsTasksOnCurrentThread());
+#endif
+  TRACE_EVENT0("blink", "TimerBase::moveToNewTaskRunner");

[Sami, 2016/12/07 18:58:13]

Might want to check if we're already on |taskRunner| (tip: you can compare the
underlying SingleThreadedTaskRunner).

[haraken, 2016/12/08 01:37:20]

Do you really want to have the trace event? moveToNewTaskRunner is not doing
anything heavy.

[altimin, 2016/12/08 14:14:38]

Done.

[altimin, 2016/12/08 14:14:38]

Agreed, removed.

+
+  m_weakPtrFactory.revokeAll();
+
+  m_webTaskRunner = std::unique_ptr<WebTaskRunner>(taskRunner->clone());

[dcheng, 2016/12/07 18:59:57]

Nit: clone() already returns a unique_ptr, doesn't it?

[altimin, 2016/12/08 14:14:38]

Thanks.

+
+  double now = timerMonotonicallyIncreasingTime();
+  double nextFireTime = m_nextFireTime;
+  m_nextFireTime = 0;

[haraken, 2016/12/08 01:37:20]

Line 100 and 101 wouldn't be needed. I think you can just call:

  setNextFireTime(now, m_nextFireTime - now);

[altimin, 2016/12/08 14:14:38]

They are needed because of line 127. setNextFireTime compares newTime with
m_nextFireTime and does nothing if they are equal.

+
+  setNextFireTime(now, nextFireTime - now);
+}
+
 // static
 WebTaskRunner* TimerBase::getTimerTaskRunner() {
   return Platform::current()->currentThread()->scheduler()->timerTaskRunner();