Oilpan: improve ScrollableArea handling.

Source/core/paint/DeprecatedPaintLayer.cpp

Index: Source/core/paint/DeprecatedPaintLayer.cpp
diff --git a/Source/core/paint/DeprecatedPaintLayer.cpp b/Source/core/paint/DeprecatedPaintLayer.cpp
index a7f62fdf05878ef7e08871febc7ff75416491108..51d8c952813dbff32f5ce2f966e1393d3bb98b95 100644
--- a/Source/core/paint/DeprecatedPaintLayer.cpp
+++ b/Source/core/paint/DeprecatedPaintLayer.cpp
@@ -171,6 +171,9 @@ DeprecatedPaintLayer::~DeprecatedPaintLayer()
 
     if (m_reflectionInfo)
         m_reflectionInfo->destroy();
+
+    if (m_scrollableArea)
+        m_scrollableArea->dispose();
 }
 
 String DeprecatedPaintLayer::debugName() const
@@ -1442,7 +1445,7 @@ void DeprecatedPaintLayer::updateStackingNode()
 void DeprecatedPaintLayer::updateScrollableArea()
 {
     if (requiresScrollableArea())
-        m_scrollableArea = adoptPtr(new DeprecatedPaintLayerScrollableArea(*this));
+        m_scrollableArea = DeprecatedPaintLayerScrollableArea::create(*this);
     else
         m_scrollableArea = nullptr;

[haraken, 2015/06/30 10:30:35]

To avoid confusion, I'd move m_scrollableArea(nullptr) to the constructor and
add ASSERT(!m_scrollableArea) at the head of updateScrollableArea().

[sof, 2015/06/30 11:34:09]

Added assert to this and another update*() method so as have them follow the
same pattern.

 }