[New Multicolumn] Render transformed layers into multiple fragments.

Source/core/paint/LayerPainter.cpp

Index: Source/core/paint/LayerPainter.cpp
diff --git a/Source/core/paint/LayerPainter.cpp b/Source/core/paint/LayerPainter.cpp
index 2751be4e24d7570bb71356809f4c69f312115971..f61e1ec5f71b50cc8b74c461d64c50fab00804e9 100644
--- a/Source/core/paint/LayerPainter.cpp
+++ b/Source/core/paint/LayerPainter.cpp
@@ -88,7 +88,7 @@ void LayerPainter::paintLayer(GraphicsContext* context, const LayerPaintingInfo&
     paintLayerContentsAndReflection(context, paintingInfo, paintFlags);
 }
 
-void LayerPainter::paintLayerContentsAndReflection(GraphicsContext* context, const LayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
+void LayerPainter::paintLayerContentsAndReflection(GraphicsContext* context, const LayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
 {
     ASSERT(m_renderLayer.isSelfPaintingLayer() || m_renderLayer.hasSelfPaintingLayerDescendant());
 
@@ -99,7 +99,7 @@ void LayerPainter::paintLayerContentsAndReflection(GraphicsContext* context, con
         m_renderLayer.reflectionInfo()->paint(context, paintingInfo, localPaintFlags | PaintLayerPaintingReflection);
 
     localPaintFlags |= PaintLayerPaintingCompositingAllPhases;
-    paintLayerContents(context, paintingInfo, localPaintFlags);
+    paintLayerContents(context, paintingInfo, localPaintFlags, fragmentPolicy);
 }
 
 class ClipPathHelper {
@@ -169,7 +169,7 @@ private:
     GraphicsContext* m_context;
 };
 
-void LayerPainter::paintLayerContents(GraphicsContext* context, const LayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
+void LayerPainter::paintLayerContents(GraphicsContext* context, const LayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
 {
     ASSERT(m_renderLayer.isSelfPaintingLayer() || m_renderLayer.hasSelfPaintingLayerDescendant());
     ASSERT(!(paintFlags & PaintLayerAppliedTransform));
@@ -230,9 +230,12 @@ void LayerPainter::paintLayerContents(GraphicsContext* context, const LayerPaint
     LayerFragments layerFragments;
     if (shouldPaintContent || shouldPaintOutline || isPaintingOverlayScrollbars) {
         // Collect the fragments. This will compute the clip rectangles and paint offsets for each layer fragment.
-        m_renderLayer.collectFragments(layerFragments, localPaintingInfo.rootLayer, localPaintingInfo.paintDirtyRect,
-            (paintFlags & PaintLayerUncachedClipRects) ? UncachedClipRects : PaintingClipRects, IgnoreOverlayScrollbarSize,
-            shouldRespectOverflowClip(paintFlags, m_renderLayer.renderer()), &offsetFromRoot, localPaintingInfo.subPixelAccumulation);
+        ClipRectsCacheSlot cacheSlot = (paintFlags & PaintLayerUncachedClipRects) ? UncachedClipRects : PaintingClipRects;
+        ShouldRespectOverflowClip respectOverflowClip = shouldRespectOverflowClip(paintFlags, m_renderLayer.renderer());
+        if (fragmentPolicy == ForceSingleFragment)
+            m_renderLayer.appendSingleFragmentIgnoringPagination(layerFragments, localPaintingInfo.rootLayer, localPaintingInfo.paintDirtyRect, cacheSlot, IgnoreOverlayScrollbarSize, respectOverflowClip, &offsetFromRoot, localPaintingInfo.subPixelAccumulation);
+        else
+            m_renderLayer.collectFragments(layerFragments, localPaintingInfo.rootLayer, localPaintingInfo.paintDirtyRect, cacheSlot, IgnoreOverlayScrollbarSize, respectOverflowClip, &offsetFromRoot, localPaintingInfo.subPixelAccumulation);
         if (shouldPaintContent)
             shouldPaintContent = atLeastOneFragmentIntersectsDamageRect(layerFragments, localPaintingInfo, paintFlags, offsetFromRoot);
     }
@@ -401,7 +404,7 @@ void LayerPainter::paintFragmentByApplyingTransform(GraphicsContext* context, co
     // Now do a paint with the root layer shifted to be us.
     LayerPaintingInfo transformedPaintingInfo(&m_renderLayer, enclosingIntRect(transform.inverse().mapRect(paintingInfo.paintDirtyRect)), paintingInfo.paintBehavior,
         adjustedSubPixelAccumulation, paintingInfo.paintingRoot);
-    paintLayerContentsAndReflection(context, transformedPaintingInfo, paintFlags);
+    paintLayerContentsAndReflection(context, transformedPaintingInfo, paintFlags, ForceSingleFragment);
 }
 
 void LayerPainter::paintChildren(unsigned childrenToVisit, GraphicsContext* context, const LayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)