Implement will-change-based creation of layers, stacking contexts, and containing blocks

Source/platform/graphics/CompositingReasons.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CompositingReasons_h
 #define CompositingReasons_h
 
 #include "wtf/MathExtras.h"
 #include <stdint.h>
 
@@ skipping 10 matching lines @@
 const uint64_t CompositingReasonBackfaceVisibilityHidden               = UINT64_C(1) << 5;
 const uint64_t CompositingReasonActiveAnimation                        = UINT64_C(1) << 6;
 const uint64_t CompositingReasonTransitionProperty                     = UINT64_C(1) << 7;
 const uint64_t CompositingReasonFilters                                = UINT64_C(1) << 8;
 const uint64_t CompositingReasonPositionFixed                          = UINT64_C(1) << 9;
 const uint64_t CompositingReasonPositionSticky                         = UINT64_C(1) << 10;
 const uint64_t CompositingReasonOverflowScrollingTouch                 = UINT64_C(1) << 11;
 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;
 
 // Overlap reasons that require knowing what's behind you in paint-order before knowing the answer
-const uint64_t CompositingReasonAssumedOverlap                         = UINT64_C(1) << 15;
-const uint64_t CompositingReasonOverlap                                = UINT64_C(1) << 16;
-const uint64_t CompositingReasonNegativeZIndexChildren                 = UINT64_C(1) << 17;
-const uint64_t CompositingReasonOverlapsWithoutSquashingTarget         = UINT64_C(1) << 18;
+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 CompositingReasonOverlapsWithoutSquashingTarget         = UINT64_C(1) << 19;
 
 // Subtree reasons that require knowing what the status of your subtree is before knowing the answer
-const uint64_t CompositingReasonTransformWithCompositedDescendants     = UINT64_C(1) << 19;
-const uint64_t CompositingReasonOpacityWithCompositedDescendants       = UINT64_C(1) << 20;
-const uint64_t CompositingReasonMaskWithCompositedDescendants          = UINT64_C(1) << 21;
-const uint64_t CompositingReasonReflectionWithCompositedDescendants    = UINT64_C(1) << 22;
-const uint64_t CompositingReasonFilterWithCompositedDescendants        = UINT64_C(1) << 23;
-const uint64_t CompositingReasonBlendingWithCompositedDescendants      = UINT64_C(1) << 24;
-const uint64_t CompositingReasonClipsCompositingDescendants            = UINT64_C(1) << 25;
-const uint64_t CompositingReasonPerspectiveWith3DDescendants           = UINT64_C(1) << 26;
-const uint64_t CompositingReasonPreserve3DWith3DDescendants            = UINT64_C(1) << 27;
-const uint64_t CompositingReasonReflectionOfCompositedParent           = UINT64_C(1) << 28;
-const uint64_t CompositingReasonIsolateCompositedDescendants           = UINT64_C(1) << 29;
+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;
 
 // 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) << 30;
+const uint64_t CompositingReasonRoot                                   = UINT64_C(1) << 31;
 
 // CompositedLayerMapping internal hierarchy reasons
-const uint64_t CompositingReasonLayerForAncestorClip                   = UINT64_C(1) << 31;
-const uint64_t CompositingReasonLayerForDescendantClip                 = UINT64_C(1) << 32;
-const uint64_t CompositingReasonLayerForPerspective                    = UINT64_C(1) << 33;
-const uint64_t CompositingReasonLayerForHorizontalScrollbar            = UINT64_C(1) << 34;
-const uint64_t CompositingReasonLayerForVerticalScrollbar              = UINT64_C(1) << 35;
-const uint64_t CompositingReasonLayerForScrollCorner                   = UINT64_C(1) << 36;
-const uint64_t CompositingReasonLayerForScrollingContents              = UINT64_C(1) << 37;
-const uint64_t CompositingReasonLayerForScrollingContainer             = UINT64_C(1) << 38;
-const uint64_t CompositingReasonLayerForSquashingContents              = UINT64_C(1) << 39;
-const uint64_t CompositingReasonLayerForSquashingContainer             = UINT64_C(1) << 40;
-const uint64_t CompositingReasonLayerForForeground                     = UINT64_C(1) << 41;
-const uint64_t CompositingReasonLayerForBackground                     = UINT64_C(1) << 42;
-const uint64_t CompositingReasonLayerForMask                           = UINT64_C(1) << 43;
-const uint64_t CompositingReasonLayerForClippingMask                   = UINT64_C(1) << 44;
+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;
 
 // Various combinations of compositing reasons are defined here also, for more intutive and faster bitwise logic.
 const uint64_t CompositingReasonComboAllDirectReasons =
     CompositingReason3DTransform
     | CompositingReasonVideo
     | CompositingReasonCanvas
     | CompositingReasonPlugin
     | CompositingReasonIFrame
     | CompositingReasonBackfaceVisibilityHidden
     | CompositingReasonActiveAnimation
     | CompositingReasonTransitionProperty
     | CompositingReasonFilters
     | CompositingReasonPositionFixed
     | CompositingReasonPositionSticky
     | CompositingReasonOverflowScrollingTouch
     | CompositingReasonOverflowScrollingParent
     | CompositingReasonOutOfFlowClipping
-    | CompositingReasonVideoOverlay;
+    | CompositingReasonVideoOverlay
+    | CompositingReasonWillChange;
 
 const uint64_t CompositingReasonComboReasonsThatRequireOwnBacking =
     CompositingReasonComboAllDirectReasons
     | CompositingReasonOverlap
     | CompositingReasonAssumedOverlap
     | CompositingReasonNegativeZIndexChildren
     | CompositingReasonOverlapsWithoutSquashingTarget
     | CompositingReasonTransformWithCompositedDescendants
     | CompositingReasonOpacityWithCompositedDescendants
     | CompositingReasonMaskWithCompositedDescendants
@@ skipping 56 matching lines @@
         "Is a scrollable overflow element" },
     { CompositingReasonOverflowScrollingParent,
         "overflowScrollingParent",
         "Scroll parent is not an ancestor" },
     { CompositingReasonOutOfFlowClipping,
         "outOfFlowClipping",
         "Has clipping ancestor" },
     { CompositingReasonVideoOverlay,
         "videoOverlay",
         "Is overlay controls for video" },
+    { CompositingReasonWillChange,
+        "willChange",
+        "Has a will-change compositing hint" },
     { CompositingReasonAssumedOverlap,
         "assumedOverlap",
         "Might overlap other composited content" },
     { CompositingReasonOverlap,
         "overlap",
         "Overlaps other composited content" },
     { CompositingReasonNegativeZIndexChildren,
         "negativeZIndexChildren",
         "Parent with composited negative z-index content" },
     { CompositingReasonOverlapsWithoutSquashingTarget,
@@ skipping 75 matching lines @@
         "layerForMask",
         "Secondary layer, to contain the mask contents" },
     { CompositingReasonLayerForClippingMask,
         "layerForClippingMask",
         "Secondary layer, for clipping mask" }
 };
 
 } // namespace WebCore
 
 #endif // CompositingReasons_h