Fix border radius on composited children.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index 7c500884885c0045d20b7a4ca37ac354ba8e12ab..662930434c38d209cc0ee28aa51968e4d271221a 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -374,7 +374,8 @@ PaintResult PaintLayerPainter::paintLayerContents(
   // scrolling contents and scrollbars.
   if (m_paintLayer.layoutObject()->hasClipPath() &&
       (!m_paintLayer.needsCompositedScrolling() ||
-       (paintFlags & PaintLayerPaintingChildClippingMaskPhase))) {
+       (paintFlags & (PaintLayerPaintingChildClippingMaskPhase |
+                      PaintLayerPaintingAncestorClippingMaskPhase)))) {
     paintingInfo.ancestorHasClipPathClipping = true;
 
     LayoutRect referenceBox(m_paintLayer.boxForClipPath());
@@ -430,19 +431,34 @@ PaintResult PaintLayerPainter::paintLayerContents(
     // TODO(trchen): We haven't decided how to handle visual fragmentation with

[chrishtr, 2016/12/02 19:21:47]

This comment belongs down by line 446.

[Stephen Chennney, 2016/12/07 21:39:38]

Done.

     // SPv2.  Related thread
     // https://groups.google.com/a/chromium.org/forum/#!topic/graphics-dev/81XuWFf-mxM
+    PaintLayer* paintLayerForFragmentsAndClip = &m_paintLayer;
+    LayoutPoint offsetFromRootForFragmentsAndClip = offsetFromRoot;
+    if (paintFlags & PaintLayerPaintingAncestorClippingMaskPhase) {
+      // Compute fragments and their clips with respect to the clipping
+      // container, and then convert them back to this layer's space.
+      // We need a new offset from root.
+      paintLayerForFragmentsAndClip =
+          m_paintLayer.clippingContainer()->enclosingLayer();
+      paintLayerForFragmentsAndClip->convertToLayerCoords(

[chrishtr, 2016/12/02 19:21:47]

You can't map from an ancestor to a descendant PaintLayer with this method.
If that is desired, switch the two positions and negate.

[Stephen Chennney, 2016/12/07 21:39:38]

Done.

+          m_paintLayer.root(), offsetFromRootForFragmentsAndClip);
+    }
+
     if (fragmentPolicy == ForceSingleFragment ||
-        RuntimeEnabledFeatures::slimmingPaintV2Enabled())
-      m_paintLayer.appendSingleFragmentIgnoringPagination(
+        RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+      paintLayerForFragmentsAndClip->appendSingleFragmentIgnoringPagination(
           layerFragments, localPaintingInfo.rootLayer,
           localPaintingInfo.paintDirtyRect, cacheSlot,
-          IgnoreOverlayScrollbarSize, respectOverflowClip, &offsetFromRoot,
+          IgnoreOverlayScrollbarSize, respectOverflowClip,
+          &offsetFromRootForFragmentsAndClip,
           localPaintingInfo.subPixelAccumulation);
-    else
-      m_paintLayer.collectFragments(layerFragments, localPaintingInfo.rootLayer,
-                                    localPaintingInfo.paintDirtyRect, cacheSlot,
-                                    IgnoreOverlayScrollbarSize,
-                                    respectOverflowClip, &offsetFromRoot,
-                                    localPaintingInfo.subPixelAccumulation);
+    } else {
+      paintLayerForFragmentsAndClip->collectFragments(
+          layerFragments, localPaintingInfo.rootLayer,
+          localPaintingInfo.paintDirtyRect, cacheSlot,
+          IgnoreOverlayScrollbarSize, respectOverflowClip,
+          &offsetFromRootForFragmentsAndClip,
+          localPaintingInfo.subPixelAccumulation);
+    }
 
     if (shouldPaintContent) {
       // TODO(wangxianzhu): This is for old slow scrolling. Implement similar
@@ -546,7 +562,8 @@ PaintResult PaintLayerPainter::paintLayerContents(
       shouldPaintContent && m_paintLayer.layoutObject()->hasMask() &&
       !selectionOnly;
   bool shouldPaintClippingMask =
-      (paintFlags & PaintLayerPaintingChildClippingMaskPhase) &&
+      (paintFlags & (PaintLayerPaintingChildClippingMaskPhase |
+                     PaintLayerPaintingAncestorClippingMaskPhase)) &&
       shouldPaintContent && !selectionOnly;
 
   if (shouldPaintMask)
@@ -625,6 +642,7 @@ PaintResult PaintLayerPainter::paintLayerWithTransform(
       object->container() == view && view->pageLogicalHeight();
   PaintLayer* paginationLayer = m_paintLayer.enclosingPaginationLayer();
   PaintLayerFragments fragments;
+

[chrishtr, 2016/12/02 19:21:47]

Super nit: spurious.

[Stephen Chennney, 2016/12/07 21:39:38]

Done.

   // TODO(crbug.com/619094): Figure out the correct behaviour for fixed position
   // objects in paged media with vertical writing modes.
   if (isFixedPosObjectInPagedMedia && view->isHorizontalWritingMode()) {
@@ -881,6 +899,22 @@ void PaintLayerPainter::paintOverflowControlsForFragments(
   }
 }
 
+void adjustPaintOffsetForAncestorClippingMask(
+    PaintLayer& layer, LayoutPoint& paintOffset)
+{
+    // Adjust the paint offset to reflect the fact that the fragment is
+    // positioned for the clipping container object.
+    LayoutPoint clippersOffsetToRoot;
+    PaintLayer* paintLayerForMask =
+        layer.clippingContainer()->enclosingLayer();
+    paintLayerForMask->convertToLayerCoords(layer.root(),

[chrishtr, 2016/12/02 19:21:47]

This duplicates line 442 I think?

+        clippersOffsetToRoot);
+    LayoutPoint paintersOffsetToRoot;
+    layer.convertToLayerCoords(layer.root(), paintersOffsetToRoot);
+
+    paintOffset.move(paintersOffsetToRoot - clippersOffsetToRoot);
+}
+
 void PaintLayerPainter::paintFragmentWithPhase(
     PaintPhase phase,
     const PaintLayerFragment& fragment,
@@ -909,9 +943,21 @@ void PaintLayerPainter::paintFragmentWithPhase(
         break;
     }
 
-    clipRecorder.emplace(context, *m_paintLayer.layoutObject(), clipType,
-                         clipRect, &paintingInfo, fragment.paginationOffset,
-                         paintFlags, clippingRule);
+    // When painting the clipping mask for a composited child, we pass
+    // the clipping container object as the layoutObject to provide the clip.
+    // The recorder assumes the fragment is positioned in that objects's
+    // layer coordinates, so we also convert that.
+    if (paintFlags & PaintLayerPaintingAncestorClippingMaskPhase) {
+      clipRecorder.emplace(
+          context, *(toLayoutBoxModelObject(m_paintLayer.clippingContainer())),

[chrishtr, 2016/12/02 19:21:47]

Might be easier to read if you make a local variable for the clipping object:

LayoutObject* clippingObject = paintFlags &
PaintLayerPaintingAncestorClippingMaskPhase ? m_paintLayer.clippingContainer()
: m_paintLayer.layoutObject()

+          clipType, clipRect, &paintingInfo,
+          fragment.paginationOffset,
+          paintFlags, clippingRule);
+    } else {
+      clipRecorder.emplace(context, *m_paintLayer.layoutObject(), clipType,
+                           clipRect, &paintingInfo, fragment.paginationOffset,
+                           paintFlags, clippingRule);
+    }
   }
 
   LayoutRect newCullRect(clipRect.rect());
@@ -945,6 +991,9 @@ void PaintLayerPainter::paintFragmentWithPhase(
                       paintingInfo.getGlobalPaintFlags(), paintFlags,
                       paintingInfo.rootLayer->layoutObject());
 
+  if (paintFlags & PaintLayerPaintingAncestorClippingMaskPhase)
+    adjustPaintOffsetForAncestorClippingMask(m_paintLayer, paintOffset);
+
   m_paintLayer.layoutObject()->paint(paintInfo, paintOffset);
 }