[New Multicolumn] Let updatePagination() do its job also when composited.

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 455 matching lines @@
 
     if (renderer()->hasColumns())
         needsPaginationUpdate = true;
 
     for (RenderLayer* child = firstChild(); child; child = child->nextSibling())
         child->updatePaginationRecursive(needsPaginationUpdate);
 }
 
 void RenderLayer::updatePagination()
 {
-    if (compositingState() != NotComposited || !parent())
-        return; // FIXME: We will have to deal with paginated compositing layers someday.
-                // FIXME: For now the RenderView can't be paginated.  Eventually printing will move to a model where it is though.
+    bool usesRegionBasedColumns = useRegionBasedColumns();
+    if ((!usesRegionBasedColumns && compositingState() != NotComposited) || !parent())
+        return; // FIXME: For now the RenderView can't be paginated.  Eventually printing will move to a model where it is though.
 
     // The main difference between the paginated booleans for the old column code and the new column code
     // is that each paginated layer has to paint on its own with the new code. There is no
     // recurring into child layers. This means that the m_isPaginated bits for the new column code can't just be set on
     // "roots" that get split and paint all their descendants. Instead each layer has to be checked individually and
     // genuinely know if it is going to have to split itself up when painting only its contents (and not any other descendant
     // layers). We track an enclosingPaginationLayer instead of using a simple bit, since we want to be able to get back
     // to that layer easily.
-    bool regionBasedColumnsUsed = useRegionBasedColumns();
-    if (regionBasedColumnsUsed && renderer()->isRenderFlowThread()) {
+    if (usesRegionBasedColumns && renderer()->isRenderFlowThread()) {
         m_enclosingPaginationLayer = this;
         return;
     }
 
     if (m_stackingNode->isNormalFlowOnly()) {
-        if (regionBasedColumnsUsed) {
+        if (usesRegionBasedColumns) {
             // Content inside a transform is not considered to be paginated, since we simply
             // paint the transform multiple times in each column, so we don't have to use
             // fragments for the transformed content.
             m_enclosingPaginationLayer = parent()->enclosingPaginationLayer();
             if (m_enclosingPaginationLayer && m_enclosingPaginationLayer->hasTransform())
                 m_enclosingPaginationLayer = 0;
         } else {
             m_isPaginated = parent()->renderer()->hasColumns();
         }
         return;
     }
 
     // For the new columns code, we want to walk up our containing block chain looking for an enclosing layer. Once
     // we find one, then we just check its pagination status.
-    if (regionBasedColumnsUsed) {
+    if (usesRegionBasedColumns) {
         RenderView* view = renderer()->view();
         RenderBlock* containingBlock;
         for (containingBlock = renderer()->containingBlock();
              containingBlock && containingBlock != view;
              containingBlock = containingBlock->containingBlock()) {
             if (containingBlock->hasLayer()) {
                 // Content inside a transform is not considered to be paginated, since we simply
                 // paint the transform multiple times in each column, so we don't have to use
                 // fragments for the transformed content.
                 m_enclosingPaginationLayer = containingBlock->layer()->enclosingPaginationLayer();
@@ skipping 2343 matching lines @@
     }
 }
 
 void showLayerTree(const blink::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif