[New Multicolumn] Make rounded corners clipping multicol-aware.

Source/core/paint/LayerPainter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef LayerPainter_h
 #define LayerPainter_h
 
 #include "core/paint/ClipRecorder.h"
 #include "core/rendering/LayerFragment.h"
 #include "core/rendering/LayerPaintingInfo.h"
@@ skipping 12 matching lines @@
     //  paint() assumes that the caller will clip to the bounds of damageRect if necessary.
     void paint(GraphicsContext*, const LayoutRect& damageRect, PaintBehavior = PaintBehaviorNormal, RenderObject* paintingRoot = 0, PaintLayerFlags = 0);
     // paintLayer() assumes that the caller will clip to the bounds of the painting dirty if necessary.
     void paintLayer(GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags);
     // paintLayerContents() assumes that the caller will clip to the bounds of the painting dirty rect if necessary.
     void paintLayerContents(GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags);
 
     void paintOverlayScrollbars(GraphicsContext*, const LayoutRect& damageRect, PaintBehavior, RenderObject* paintingRoot = 0);
 
     enum BorderRadiusClippingRule { IncludeSelfForBorderRadius, DoNotIncludeSelfForBorderRadius };
-    static void applyRoundedRectClips(RenderLayer&, const LayerPaintingInfo&, GraphicsContext*, PaintLayerFlags, ClipRecorder&, BorderRadiusClippingRule = IncludeSelfForBorderRadius);
+
+    // Set rounded clip rectangles defined by border radii all the way from the LayerPaintingInfo
+    // "root" layer down to the specified layer (or the parent of said layer, in case
+    // BorderRadiusClippingRule says to skip self). fragmentOffset is used for multicol, to specify
+    // the translation required to get from flow thread coordinates to visual coordinates for a
+    // certain column.
+    // FIXME: The BorderRadiusClippingRule parameter is really useless now. If we want to skip self,
+    // why not just supply the parent layer as the first parameter instead?
+    static void applyRoundedRectClips(RenderLayer&, const LayerPaintingInfo&, GraphicsContext*, const LayoutPoint& fragmentOffset, PaintLayerFlags, ClipRecorder&, BorderRadiusClippingRule = IncludeSelfForBorderRadius);
 
 private:
     enum ClipState { HasNotClipped, HasClipped };
 
     void paintLayerContentsAndReflection(GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags);
     void paintLayerByApplyingTransform(GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags, const LayoutPoint& translationOffset = LayoutPoint());
 
     void paintChildren(unsigned childrenToVisit, GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags);
     void paintPaginatedChildLayer(RenderLayer* childLayer, GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags);
     void paintChildLayerIntoColumns(RenderLayer* childLayer, GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags, const Vector<RenderLayer*>& columnLayers, size_t columnIndex);
@@ skipping 18 matching lines @@
     // layers).
     bool shouldPaintLayerInSoftwareMode(const LayerPaintingInfo&, PaintLayerFlags paintFlags);
     bool shouldCreateTransparencyLayerForBlendMode();
 
     RenderLayer& m_renderLayer;
 };
 
 } // namespace blink
 
 #endif // LayerPainter_h