Use the bounding box of all descendants for localVisualRect if there is a mask.

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

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index 552fcb53bae7c62861a5ba181e2a454e0944a562..e1996a4c26dd98496167a80bbab5e6e8f2430eb8 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -2339,7 +2339,7 @@ PaintLayer* PaintLayer::hitTestChildren(
   return resultLayer;
 }
 
-FloatRect PaintLayer::boxForFilter() const {
+FloatRect PaintLayer::boxForFilterOrMask() const {
   return FloatRect(physicalBoundingBoxIncludingStackingChildren(
       LayoutPoint(), PaintLayer::CalculateBoundsOptions::
                          IncludeTransformsAndCompositedChildLayers));
@@ -3022,7 +3022,7 @@ PaintLayer::createCompositorFilterOperationsForFilter(
     const ComputedStyle& style) {
   FloatRect zoomedReferenceBox;
   if (style.filter().hasReferenceFilter())
-    zoomedReferenceBox = boxForFilter();
+    zoomedReferenceBox = boxForFilterOrMask();
   FilterEffectBuilder builder(enclosingNode(), zoomedReferenceBox,
                               style.effectiveZoom());
   return builder.buildFilterOperations(addReflectionToFilterOperations(style));
@@ -3033,7 +3033,7 @@ PaintLayer::createCompositorFilterOperationsForBackdropFilter(
     const ComputedStyle& style) {
   FloatRect zoomedReferenceBox;
   if (style.backdropFilter().hasReferenceFilter())
-    zoomedReferenceBox = boxForFilter();
+    zoomedReferenceBox = boxForFilterOrMask();
   FilterEffectBuilder builder(enclosingNode(), zoomedReferenceBox,
                               style.effectiveZoom());
   return builder.buildFilterOperations(style.backdropFilter());
@@ -3081,7 +3081,7 @@ FilterEffect* PaintLayer::lastFilterEffect() const {
   const ComputedStyle& style = layoutObject()->styleRef();
   FloatRect zoomedReferenceBox;
   if (style.filter().hasReferenceFilter())
-    zoomedReferenceBox = boxForFilter();
+    zoomedReferenceBox = boxForFilterOrMask();
   FilterEffectBuilder builder(enclosingNode(), zoomedReferenceBox,
                               style.effectiveZoom());
   resourceInfo->setLastEffect(