Suppress layer creation for descendants of GPU-rasterized layers

Source/platform/graphics/CompositingReasons.h

Index: Source/platform/graphics/CompositingReasons.h
diff --git a/Source/platform/graphics/CompositingReasons.h b/Source/platform/graphics/CompositingReasons.h
index ca030e4491e64a3d4f25fb97b7e37f88b432a0e9..811378c54586608efb7a654681ab9fe7032750ca 100644
--- a/Source/platform/graphics/CompositingReasons.h
+++ b/Source/platform/graphics/CompositingReasons.h
@@ -29,46 +29,47 @@ const uint64_t CompositingReasonOverflowScrollingTouch                 = UINT64_
 const uint64_t CompositingReasonOverflowScrollingParent                = UINT64_C(1) << 12;
 const uint64_t CompositingReasonOutOfFlowClipping                      = UINT64_C(1) << 13;
 const uint64_t CompositingReasonVideoOverlay                           = UINT64_C(1) << 14;
-const uint64_t CompositingReasonWillChange                             = UINT64_C(1) << 15;
+const uint64_t CompositingReasonWillChangeCompositingHint              = UINT64_C(1) << 15;
+const uint64_t CompositingReasonWillChangeGpuRasterizationHint         = UINT64_C(1) << 16;
 
 // Overlap reasons that require knowing what's behind you in paint-order before knowing the answer
-const uint64_t CompositingReasonAssumedOverlap                         = UINT64_C(1) << 16;
-const uint64_t CompositingReasonOverlap                                = UINT64_C(1) << 17;
-const uint64_t CompositingReasonNegativeZIndexChildren                 = UINT64_C(1) << 18;
-const uint64_t CompositingReasonNoSquashingTargetFound                 = UINT64_C(1) << 19;
+const uint64_t CompositingReasonAssumedOverlap                         = UINT64_C(1) << 17;
+const uint64_t CompositingReasonOverlap                                = UINT64_C(1) << 18;
+const uint64_t CompositingReasonNegativeZIndexChildren                 = UINT64_C(1) << 19;
+const uint64_t CompositingReasonNoSquashingTargetFound                 = UINT64_C(1) << 20;
 
 // Subtree reasons that require knowing what the status of your subtree is before knowing the answer
-const uint64_t CompositingReasonTransformWithCompositedDescendants     = UINT64_C(1) << 20;
-const uint64_t CompositingReasonOpacityWithCompositedDescendants       = UINT64_C(1) << 21;
-const uint64_t CompositingReasonMaskWithCompositedDescendants          = UINT64_C(1) << 22;
-const uint64_t CompositingReasonReflectionWithCompositedDescendants    = UINT64_C(1) << 23;
-const uint64_t CompositingReasonFilterWithCompositedDescendants        = UINT64_C(1) << 24;
-const uint64_t CompositingReasonBlendingWithCompositedDescendants      = UINT64_C(1) << 25;
-const uint64_t CompositingReasonClipsCompositingDescendants            = UINT64_C(1) << 26;
-const uint64_t CompositingReasonPerspectiveWith3DDescendants           = UINT64_C(1) << 27;
-const uint64_t CompositingReasonPreserve3DWith3DDescendants            = UINT64_C(1) << 28;
-const uint64_t CompositingReasonReflectionOfCompositedParent           = UINT64_C(1) << 29;
-const uint64_t CompositingReasonIsolateCompositedDescendants           = UINT64_C(1) << 30;
+const uint64_t CompositingReasonTransformWithCompositedDescendants     = UINT64_C(1) << 21;
+const uint64_t CompositingReasonOpacityWithCompositedDescendants       = UINT64_C(1) << 22;
+const uint64_t CompositingReasonMaskWithCompositedDescendants          = UINT64_C(1) << 23;
+const uint64_t CompositingReasonReflectionWithCompositedDescendants    = UINT64_C(1) << 24;
+const uint64_t CompositingReasonFilterWithCompositedDescendants        = UINT64_C(1) << 25;
+const uint64_t CompositingReasonBlendingWithCompositedDescendants      = UINT64_C(1) << 26;
+const uint64_t CompositingReasonClipsCompositingDescendants            = UINT64_C(1) << 27;
+const uint64_t CompositingReasonPerspectiveWith3DDescendants           = UINT64_C(1) << 28;
+const uint64_t CompositingReasonPreserve3DWith3DDescendants            = UINT64_C(1) << 29;
+const uint64_t CompositingReasonReflectionOfCompositedParent           = UINT64_C(1) << 30;
+const uint64_t CompositingReasonIsolateCompositedDescendants           = UINT64_C(1) << 31;
 
 // The root layer is a special case that may be forced to be a layer, but also it needs to be
 // a layer if anything else in the subtree is composited.
-const uint64_t CompositingReasonRoot                                   = UINT64_C(1) << 31;
+const uint64_t CompositingReasonRoot                                   = UINT64_C(1) << 32;
 
 // CompositedLayerMapping internal hierarchy reasons
-const uint64_t CompositingReasonLayerForAncestorClip                   = UINT64_C(1) << 32;
-const uint64_t CompositingReasonLayerForDescendantClip                 = UINT64_C(1) << 33;
-const uint64_t CompositingReasonLayerForPerspective                    = UINT64_C(1) << 34;
-const uint64_t CompositingReasonLayerForHorizontalScrollbar            = UINT64_C(1) << 35;
-const uint64_t CompositingReasonLayerForVerticalScrollbar              = UINT64_C(1) << 36;
-const uint64_t CompositingReasonLayerForScrollCorner                   = UINT64_C(1) << 37;
-const uint64_t CompositingReasonLayerForScrollingContents              = UINT64_C(1) << 38;
-const uint64_t CompositingReasonLayerForScrollingContainer             = UINT64_C(1) << 39;
-const uint64_t CompositingReasonLayerForSquashingContents              = UINT64_C(1) << 40;
-const uint64_t CompositingReasonLayerForSquashingContainer             = UINT64_C(1) << 41;
-const uint64_t CompositingReasonLayerForForeground                     = UINT64_C(1) << 42;
-const uint64_t CompositingReasonLayerForBackground                     = UINT64_C(1) << 43;
-const uint64_t CompositingReasonLayerForMask                           = UINT64_C(1) << 44;
-const uint64_t CompositingReasonLayerForClippingMask                   = UINT64_C(1) << 45;
+const uint64_t CompositingReasonLayerForAncestorClip                   = UINT64_C(1) << 33;
+const uint64_t CompositingReasonLayerForDescendantClip                 = UINT64_C(1) << 34;
+const uint64_t CompositingReasonLayerForPerspective                    = UINT64_C(1) << 35;
+const uint64_t CompositingReasonLayerForHorizontalScrollbar            = UINT64_C(1) << 36;
+const uint64_t CompositingReasonLayerForVerticalScrollbar              = UINT64_C(1) << 37;
+const uint64_t CompositingReasonLayerForScrollCorner                   = UINT64_C(1) << 38;
+const uint64_t CompositingReasonLayerForScrollingContents              = UINT64_C(1) << 39;
+const uint64_t CompositingReasonLayerForScrollingContainer             = UINT64_C(1) << 40;
+const uint64_t CompositingReasonLayerForSquashingContents              = UINT64_C(1) << 41;
+const uint64_t CompositingReasonLayerForSquashingContainer             = UINT64_C(1) << 42;
+const uint64_t CompositingReasonLayerForForeground                     = UINT64_C(1) << 43;
+const uint64_t CompositingReasonLayerForBackground                     = UINT64_C(1) << 44;
+const uint64_t CompositingReasonLayerForMask                           = UINT64_C(1) << 45;
+const uint64_t CompositingReasonLayerForClippingMask                   = UINT64_C(1) << 46;
 
 // Various combinations of compositing reasons are defined here also, for more intutive and faster bitwise logic.
 const uint64_t CompositingReasonComboAllDirectReasons =
@@ -87,7 +88,8 @@ const uint64_t CompositingReasonComboAllDirectReasons =
     | CompositingReasonOverflowScrollingParent
     | CompositingReasonOutOfFlowClipping
     | CompositingReasonVideoOverlay
-    | CompositingReasonWillChange;
+    | CompositingReasonWillChangeCompositingHint
+    | CompositingReasonWillChangeGpuRasterizationHint;
 
 const uint64_t CompositingReasonComboAllStyleDeterminedReasons =
     CompositingReason3DTransform
@@ -95,7 +97,8 @@ const uint64_t CompositingReasonComboAllStyleDeterminedReasons =
     | CompositingReasonActiveAnimation
     | CompositingReasonTransitionProperty
     | CompositingReasonFilters
-    | CompositingReasonWillChange;
+    | CompositingReasonWillChangeCompositingHint
+    | CompositingReasonWillChangeGpuRasterizationHint;
 
 const uint64_t CompositingReasonComboReasonsThatRequireOwnBacking =
     CompositingReasonComboAllDirectReasons
@@ -187,9 +190,12 @@ static const CompositingReasonStringMap compositingReasonStringMap[] = {
     { CompositingReasonVideoOverlay,
         "videoOverlay",
         "Is overlay controls for video" },
-    { CompositingReasonWillChange,
+    { CompositingReasonWillChangeCompositingHint,
         "willChange",
         "Has a will-change compositing hint" },
+    { CompositingReasonWillChangeGpuRasterizationHint,
+        "willChange",
+        "Has a will-change GPU-rasterization hint" },
     { CompositingReasonAssumedOverlap,
         "assumedOverlap",
         "Might overlap other composited content" },