Fix border radius on composited children.

third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp b/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
index 214c5beccd500073757151192bf0383e8f21fb45..d36d6165fd64bb7a93b872befb38cb0d0f673e69 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
@@ -189,7 +189,7 @@ LayoutRect PaintLayerClipper::localClipRect(const PaintLayer* clippingRootLayer)
 }
 
 void PaintLayerClipper::calculateRects(const ClipRectsContext& context, const LayoutRect& paintDirtyRect, LayoutRect& layerBounds,
-    ClipRect& backgroundRect, ClipRect& foregroundRect, const LayoutPoint* offsetFromRoot) const
+    ClipRect& backgroundRect, ClipRect& foregroundRect, const LayoutPoint* offsetFromRoot, const bool addAncestorClips) const
 {
     bool isClippingRoot = &m_layer == context.rootLayer;
     LayoutBoxModelObject& layoutObject = *m_layer.layoutObject();
@@ -212,9 +212,9 @@ void PaintLayerClipper::calculateRects(const ClipRectsContext& context, const La
     layerBounds = LayoutRect(offset, LayoutSize(m_layer.size()));
 
     // Update the clip rects that will be passed to child layers.
-    if ((layoutObject.hasOverflowClip() || layoutObject.styleRef().containsPaint()) && shouldRespectOverflowClip(context)) {
+    if (addAncestorClips || ((layoutObject.hasOverflowClip() || layoutObject.styleRef().containsPaint()) && shouldRespectOverflowClip(context))) {
         foregroundRect.intersect(toLayoutBox(layoutObject).overflowClipRect(offset, context.overlayScrollbarClipBehavior));
-        if (layoutObject.styleRef().hasBorderRadius())
+        if (layoutObject.styleRef().hasBorderRadius() || addAncestorClips)

[chrishtr, 2016/10/21 23:16:20]

What does this one achieve? It seems to force setting radius to true, which
can't be true for all masks?

[Stephen Chennney, 2016/10/24 20:15:27]

This is the hackish part of the whole thing. It's relying on the fact that the
only way addAncestorClips can be true is if, sometime back in
CompositedLayerMapping, we discovered a border radius clip and added a layer and
added a paint phase etc etc.

It's one of the things I want to improve.

             foregroundRect.setHasRadius(true);
 
         // FIXME: Does not do the right thing with columns yet, since we don't yet factor in the