Oilpan: persist Timer<T>'s object while active.

Source/platform/Timer.cpp

Index: Source/platform/Timer.cpp
diff --git a/Source/platform/Timer.cpp b/Source/platform/Timer.cpp
index 202365017771b305dbafcb84c88fd974caeecf8d..5e696440e9d6b07b1ff5f74e2a5e10e1394be961 100644
--- a/Source/platform/Timer.cpp
+++ b/Source/platform/Timer.cpp
@@ -402,7 +402,7 @@ void TimerBase::fireTimersInNestedEventLoop()
 
 void TimerBase::didChangeAlignmentInterval()
 {
-    setNextFireTime(m_unalignedNextFireTime);
+    this->setNextFireTime(m_unalignedNextFireTime);
 }
 
 double TimerBase::nextUnalignedFireInterval() const
@@ -411,4 +411,50 @@ double TimerBase::nextUnalignedFireInterval() const
     return std::max(m_unalignedNextFireTime - monotonicallyIncreasingTime(), 0.0);
 }
 
+namespace {
+
+class ActiveTimerInstanceTracker final : public GarbageCollectedFinalized<ActiveTimerInstanceTracker> {
+public:
+    void add(const void* self, TimerInstanceTracker::TraceMethodTrampoline trampoline)
+    {
+        m_activeTimerInstances.add(self, trampoline);
+    }
+
+    void remove(const void* self)
+    {
+        m_activeTimerInstances.remove(self);
+    }
+
+    void trace(Visitor* visitor)
+    {
+        for (const auto& active : m_activeTimerInstances)
+            active.value(visitor, const_cast<void*>(active.key));
+    }
+
+private:
+    using ActiveTimerInstanceMap = HashMap<const void*, TimerInstanceTracker::TraceMethodTrampoline>;
+
+    ActiveTimerInstanceMap m_activeTimerInstances;
+};
+
+static ActiveTimerInstanceTracker& activeTimerInstanceTracker()
+{
+    DEFINE_STATIC_LOCAL(Persistent<ActiveTimerInstanceTracker>, tracker, (new ActiveTimerInstanceTracker));
+    return *tracker;
+}
+
+}
+
+void TimerInstanceTracker::add(const void* self, TraceMethodTrampoline trampoline)
+{
+    ActiveTimerInstanceTracker& tracker = activeTimerInstanceTracker();
+    tracker.add(self, trampoline);
+}
+
+void TimerInstanceTracker::remove(const void* self)
+{
+    ActiveTimerInstanceTracker& tracker = activeTimerInstanceTracker();
+    tracker.remove(self);
+}
+
 } // namespace blink