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 e1c8fdce368965828ee0faf852f8e417f6fe30fb..388ef49fd8c5c23e62d4c4ab754c3a035fd66f11 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -229,6 +229,27 @@ static bool shouldRepaintSubsequence(
   return needsRepaint;
 }
 
+LayoutPoint PaintLayerPainter::fragmentOffsetForAncestorClipMask(
+    const LayoutPoint& originalFragmentOffset) {
+  // The clipping container that will be used to define the clip and the
+  // child layer with respect to which the fragment offset is defined share
+  // a layer root. When the clip is recorded we will be using the clipping
+  // container's layer's offset to the root to position the clip. Hence we
+  // must convert the fragment offset into a corresponding offset in the
+  // clipping container's layer coordinates. To do that, we find the
+  // originalFragmentOffset's coordinate in the root layer, fragmentDelta.
+  // We also find the offset of the clipping container's origin in the root
+  // layer's coordinates, clippingDelta. clippingDelta - fragmentDelta gives
+  // the fragment's position in the root layer. But we need the position in
+  // the clipping layer coords, and we subtract clippingDelta to get that. The
+  // resulting offset is -fragmentDelta.
+  DCHECK_EQ(m_paintLayer.root(),
+            m_paintLayer.clippingContainer()->enclosingLayer()->root());
+  LayoutPoint fragmentDelta(originalFragmentOffset);
+  m_paintLayer.convertToLayerCoords(m_paintLayer.root(), fragmentDelta);
+  return LayoutPoint(-fragmentDelta.x(), -fragmentDelta.y());
+}
+
 PaintResult PaintLayerPainter::paintLayerContents(
     GraphicsContext& context,
     const PaintLayerPaintingInfo& paintingInfoArg,
@@ -353,7 +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());
@@ -409,19 +431,48 @@ PaintResult PaintLayerPainter::paintLayerContents(
     // TODO(trchen): We haven't decided how to handle visual fragmentation with
     // 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();
+      LayoutPoint clippersOffsetToRoot;
+      paintLayerForFragmentsAndClip->convertToLayerCoords(m_paintLayer.root(),
+                                                          clippersOffsetToRoot);
+      LayoutPoint thisOffsetToRoot;
+      m_paintLayer.convertToLayerCoords(m_paintLayer.root(), thisOffsetToRoot);
+      offsetFromRootForFragmentsAndClip =
+          LayoutPoint(clippersOffsetToRoot.x() - thisOffsetToRoot.x(),
+                      clippersOffsetToRoot.y() - thisOffsetToRoot.y());
+    }
+
     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);
+    }
+
+    // Reset the layerBounds because they were set using the clipper's layer
+    if (paintFlags & PaintLayerPaintingAncestorClippingMaskPhase) {
+      for (auto& fragment : layerFragments) {
+        fragment.layerBounds =
+            LayoutRect(offsetFromRoot, LayoutSize(m_paintLayer.size()));
+      }
+    }
 
     if (shouldPaintContent) {
       // TODO(wangxianzhu): This is for old slow scrolling. Implement similar
@@ -525,7 +576,8 @@ PaintResult PaintLayerPainter::paintLayerContents(
       shouldPaintContent && m_paintLayer.layoutObject()->hasMask() &&
       !selectionOnly;
   bool shouldPaintClippingMask =
-      (paintFlags & PaintLayerPaintingChildClippingMaskPhase) &&
+      (paintFlags & (PaintLayerPaintingChildClippingMaskPhase |
+                     PaintLayerPaintingAncestorClippingMaskPhase)) &&
       shouldPaintContent && !selectionOnly;
 
   if (shouldPaintMask)
@@ -604,6 +656,7 @@ PaintResult PaintLayerPainter::paintLayerWithTransform(
       object->container() == view && view->pageLogicalHeight();
   PaintLayer* paginationLayer = m_paintLayer.enclosingPaginationLayer();
   PaintLayerFragments fragments;
+
   // TODO(crbug.com/619094): Figure out the correct behaviour for fixed position
   // objects in paged media with vertical writing modes.
   if (isFixedPosObjectInPagedMedia && view->isHorizontalWritingMode()) {
@@ -888,9 +941,21 @@ 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())),
+          clipType, clipRect, &paintingInfo,
+          fragmentOffsetForAncestorClipMask(fragment.paginationOffset),
+          paintFlags, clippingRule);
+    } else {
+      clipRecorder.emplace(context, *m_paintLayer.layoutObject(), clipType,
+                           clipRect, &paintingInfo, fragment.paginationOffset,
+                           paintFlags, clippingRule);
+    }
   }
 
   LayoutRect newCullRect(clipRect.rect());