[Oilpan] Move ScrollAnimators onto oilpan heap

third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  * Copyright (C) 2008, 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 36 matching lines @@
 static const int kPixelsPerLineStep = 40;
 static const float kMinFractionToStepWhenPaging = 0.875f;
 
 namespace blink {
 
 struct SameSizeAsScrollableArea {
     virtual ~SameSizeAsScrollableArea();
 #if ENABLE(ASSERT) && ENABLE(OILPAN)
     VerifyEagerFinalization verifyEager;
 #endif
-    void* pointer;
+    OwnPtrWillBeMember<void*> pointer[2];
     unsigned bitfields : 16;
     IntPoint origin;
 };
 
 static_assert(sizeof(ScrollableArea) == sizeof(SameSizeAsScrollableArea), "ScrollableArea should stay small");
 
 int ScrollableArea::pixelsPerLineStep()
 {
     return kPixelsPerLineStep;
 }
@@ skipping 18 matching lines @@
     , m_scrollCornerNeedsPaintInvalidation(false)
 {
 }
 
 ScrollableArea::~ScrollableArea()
 {
 }
 
 void ScrollableArea::clearScrollAnimators()
 {
-    m_animators.clear();
+#if OS(MACOSX) && ENABLE(OILPAN)

[peria, 2015/12/03 13:42:08]

This clearing is added to make the probability to kick the timer in
ScrollAnimatorMac small.

[haraken, 2015/12/03 14:48:47]

Add something to make the likelihood small sounds bad, since it means that we
have a bug...

In oilpan, why do we need to explicitly call cleanup() here? Given the following
facts, it should not happen that the ScrollAnimator's timer is invoked after the
ScrollableArea dies.

- Both ScrollAnimator and ScrollableArea are on oilpan's heap.
- The ScrollAnimator has a strong reference to the ScrollableArea. Thus it
should not happen that the ScrollableArea dies before the ScrollAnimator.
- If the ScrollableArea and the ScrollAnimator die in the same GC cycle (this
can happen), the ScrollAnimator's pre-finalizer runs cleanup() and stops the
timer. Thus the timer should not be triggered after the ScrollableArea gets
destructed.

In conclusion, I think that we don't need to call cleanup() here. Am I missing
something?

+    if (m_scrollAnimator)
+        m_scrollAnimator->cleanup();
+#endif
+    m_scrollAnimator.clear();
+    m_programmaticScrollAnimator.clear();
 }
 
 ScrollAnimatorBase* ScrollableArea::scrollAnimator() const
 {
-    if (!m_animators)
-        m_animators = adoptPtr(new ScrollableAreaAnimators);
+    if (!m_scrollAnimator)
+        m_scrollAnimator = ScrollAnimatorBase::create(const_cast<ScrollableArea*>(this));
 
-    if (!m_animators->scrollAnimator)
-        m_animators->scrollAnimator = ScrollAnimatorBase::create(const_cast<ScrollableArea*>(this));
-
-    return m_animators->scrollAnimator.get();
+    return m_scrollAnimator.get();
 }
 
 ProgrammaticScrollAnimator* ScrollableArea::programmaticScrollAnimator() const
 {
-    if (!m_animators)
-        m_animators = adoptPtr(new ScrollableAreaAnimators);
+    if (!m_programmaticScrollAnimator)
+        m_programmaticScrollAnimator = ProgrammaticScrollAnimator::create(const_cast<ScrollableArea*>(this));
 
-    if (!m_animators->programmaticScrollAnimator)
-        m_animators->programmaticScrollAnimator = ProgrammaticScrollAnimator::create(const_cast<ScrollableArea*>(this));
-
-    return m_animators->programmaticScrollAnimator.get();
+    return m_programmaticScrollAnimator.get();
 }
 
 void ScrollableArea::setScrollOrigin(const IntPoint& origin)
 {
     if (m_scrollOrigin != origin) {
         m_scrollOrigin = origin;
         m_scrollOriginChanged = true;
     }
 }
 
@@ skipping 448 matching lines @@
     if (Scrollbar* verticalBar = verticalScrollbar())
         verticalScrollbarWidth = !verticalBar->isOverlayScrollbar() ? verticalBar->width() : 0;
     if (Scrollbar* horizontalBar = horizontalScrollbar())
         horizontalScrollbarHeight = !horizontalBar->isOverlayScrollbar() ? horizontalBar->height() : 0;
 
     return IntSize(std::max(0, size.width() - verticalScrollbarWidth),
         std::max(0, size.height() - horizontalScrollbarHeight));
 
 }
 
+DEFINE_TRACE(ScrollableArea)
+{
+    visitor->trace(m_scrollAnimator);
+    visitor->trace(m_programmaticScrollAnimator);
+}
+
 } // namespace blink