Oilpan: Move more code of RenderObject destructors to destroy().

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index 7a4db09eda33c4fdc5d87bc6e6582270b9c086ae..fb4dd16de83b758328d9a3be7075a17a4c9e7fa3 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -216,7 +216,7 @@ static void appendImagesFromStyle(Vector<ImageResource*>& images, RenderStyle& b
         appendImageIfNotNull(images, blockStyle.shapeOutside()->image());
 }
 
-RenderBlock::~RenderBlock()
+void RenderBlock::removeFromGlobalMaps()
 {
     if (hasColumns())
         gColumnInfoMap->take(this);
@@ -226,6 +226,22 @@ RenderBlock::~RenderBlock()
         removeBlockFromDescendantAndContainerMaps(this, gPositionedDescendantsMap, gPositionedContainerMap);
 }
 
+RenderBlock::~RenderBlock()
+{
+#if !ENABLE(OILPAN)
+    removeFromGlobalMaps();

[haraken, 2014/08/12 08:08:15]

Can't we call removeFromGlobalMaps() in destroy() in non-oilpan builds as well?
We don't want to have different call paths between oilpan builds and non-oilpan
builds if possible.

[tkent, 2014/08/12 08:37:51]

We can't.  |this| is deleted in destroy().

+#endif
+}
+
+void RenderBlock::destroy()
+{
+    RenderBox::destroy();

[haraken, 2014/08/12 08:08:15]

Nit: Make the destroy call to the parent class a tail call (just for consistency
with other destroy methods).

[tkent, 2014/08/12 08:37:51]

We can't do it.  destroy() depends on the global maps.

[haraken, 2014/08/12 08:47:00]

I understand what's going on. Then it seems to me that it would be better to
keep removeFromGlobalMaps() in ~RenderBlock(), because conceptually
removeFromGlobalMaps() must be called after the RenderBlock becomes unreachable.

With your CL, once we have the following code, we'll hit a crash:

class RenderSomething : public RenderBlock {
  void destroy() {
    RenderBlock::destroy();
    doSomething();
  }
};

(In the future, we should replace those global maps with weak maps of
RenderObjects.)

+#if ENABLE(OILPAN)
+    // RenderObject::removeChild called in destory() depends on gColumnInfoMap.
+    removeFromGlobalMaps();
+#endif
+}
+
 void RenderBlock::willBeDestroyed()
 {
     // Mark as being destroyed to avoid trouble with merges in removeChild().