mix-blend-mode implementation for accelerated layers - blink part

Source/core/rendering/CompositingReasons.h

Index: Source/core/rendering/CompositingReasons.h
diff --git a/Source/core/rendering/CompositingReasons.h b/Source/core/rendering/CompositingReasons.h
index 21a545ed56bb0face64e0100b3480bf15338bf16..b07999070b27507415902b218d9fd505954707b0 100644
--- a/Source/core/rendering/CompositingReasons.h
+++ b/Source/core/rendering/CompositingReasons.h
@@ -60,6 +60,7 @@ const uint64_t CompositingReasonOverflowScrollingParent                = UINT64_
 const uint64_t CompositingReasonOutOfFlowClipping                      = UINT64_C(1) << 33;
 
 const uint64_t CompositingReasonLayerForVideoOverlay                   = UINT64_C(1) << 34;
+const uint64_t CompositingReasonIsolateCompositedDescendants           = UINT64_C(1) << 35;
 
 const uint64_t CompositingReasonComboAllDirectReasons =
     CompositingReason3DTransform
@@ -86,6 +87,7 @@ const uint64_t CompositingReasonComboReasonsThatRequireOwnBacking =
     | CompositingReasonMaskWithCompositedDescendants
     | CompositingReasonFilterWithCompositedDescendants
     | CompositingReasonBlendingWithCompositedDescendants
+    | CompositingReasonIsolateCompositedDescendants
     | CompositingReasonPreserve3D; // preserve-3d has to create backing store to ensure that 3d-transformed elements intersect.
 
 // Note: if you add more reasons here, you will need to update WebCompositingReasons as well.