Fix clipping of squashed sibling layers with border radius masks

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 f9320de2ecbc1121d69e6f67d14d7989fe630dc2..0a6cd48300b7e41f78ac9b20ab5826a3b42661dc 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -964,6 +964,13 @@ void PaintLayerPainter::PaintFragmentWithPhase(
       case kPaintPhaseMask:  // Mask painting will handle clipping to self.
         clipping_rule = LayerClipRecorder::kDoNotIncludeSelfForBorderRadius;
         break;
+      case kPaintPhaseClippingMask:
+        if (paint_flags & kPaintLayerPaintingAncestorClippingMaskPhase) {
+          // The ancestor is the thing that needs to clip, so do not include
+          // this layer's clips.
+          clipping_rule = LayerClipRecorder::kDoNotIncludeSelfForBorderRadius;
+          break;
+        }
       default:
         clipping_rule = LayerClipRecorder::kIncludeSelfForBorderRadius;
         break;