[SPv2] Add CSS mask support

third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp
index e6b4a2d2fbccebabffc1f04741613a76f531e207..8e12a8a4cff4cb64ef531c9bf70c6e96e2c131c1 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp
@@ -178,17 +178,32 @@ bool CompositingReasonFinder::requiresCompositingForAnimation(
   return style.shouldCompositeForCurrentAnimations();
 }
 
-bool CompositingReasonFinder::requiresCompositingForEffectAnimation(
+bool CompositingReasonFinder::requiresCompositingForOpacityAnimation(
     const ComputedStyle& style) {
-  if (style.subtreeWillChangeContents()) {
-    return style.isRunningOpacityAnimationOnCompositor() ||
-           style.isRunningFilterAnimationOnCompositor() ||
-           style.isRunningBackdropFilterAnimationOnCompositor();
-  }
+  return style.subtreeWillChangeContents()
+             ? style.isRunningOpacityAnimationOnCompositor()
+             : style.hasCurrentOpacityAnimation();
+}
+
+bool CompositingReasonFinder::requiresCompositingForFilterAnimation(
+    const ComputedStyle& style) {
+  return style.subtreeWillChangeContents()
+             ? style.isRunningFilterAnimationOnCompositor()
+             : style.hasCurrentFilterAnimation();
+}
 
-  return style.hasCurrentOpacityAnimation() ||
-         style.hasCurrentFilterAnimation() ||
-         style.hasCurrentBackdropFilterAnimation();
+bool CompositingReasonFinder::requiresCompositingForBackdropFilterAnimation(
+    const ComputedStyle& style) {
+  return style.subtreeWillChangeContents()
+             ? style.isRunningBackdropFilterAnimationOnCompositor()
+             : style.hasCurrentBackdropFilterAnimation();
+}
+
+bool CompositingReasonFinder::requiresCompositingForEffectAnimation(
+    const ComputedStyle& style) {
+  return requiresCompositingForOpacityAnimation(style) ||
+         requiresCompositingForFilterAnimation(style) ||
+         requiresCompositingForBackdropFilterAnimation(style);
 }
 
 bool CompositingReasonFinder::requiresCompositingForTransformAnimation(