(WIP) Paint invalidation for slimming paint v2

Source/core/dom/DocumentLifecycle.cpp

Index: Source/core/dom/DocumentLifecycle.cpp
diff --git a/Source/core/dom/DocumentLifecycle.cpp b/Source/core/dom/DocumentLifecycle.cpp
index df8a50ab29080719d428eb1fcfcc92ca7be4119c..9062aa8e29023450e293add96fc54306169ecd4c 100644
--- a/Source/core/dom/DocumentLifecycle.cpp
+++ b/Source/core/dom/DocumentLifecycle.cpp
@@ -183,12 +183,16 @@ bool DocumentLifecycle::canAdvanceTo(State nextState) const
             return true;
         if (nextState == InCompositingUpdate)
             return true;
-        if (nextState == InPaintInvalidation)
+        if (nextState == InPaintInvalidation && !RuntimeEnabledFeatures::slimmingPaintV2Enabled())
+            return true;
+        if (nextState == InPaintForSlimmingPaintV2 && RuntimeEnabledFeatures::slimmingPaintV2Enabled())
             return true;
         break;
     case InPaintInvalidation:
+        ASSERT(!RuntimeEnabledFeatures::slimmingPaintV2Enabled());
         return nextState == PaintInvalidationClean;
     case PaintInvalidationClean:
+        ASSERT(!RuntimeEnabledFeatures::slimmingPaintV2Enabled());
         if (nextState == InStyleRecalc)
             return true;
         if (nextState == InPreLayout)