Fix assertions related to floats and z-order lists when compositing opaque scrollers

third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 3341 matching lines @@
         FloatingObject& floatingObject = **it;
         if (!floatBoxIsSelfPaintingLayer) {
             // This repeats the logic in addOverhangingFloats() about shouldPaint flag:
             // - The nearest enclosing block in which the float doesn't overhang paints the float;
             // - Or even if the float overhangs, if the ancestor block has self-painting layer, it
             //   paints the float.
             if (ancestorBlock->hasSelfPaintingLayer() || !ancestorBlock->isOverhangingFloat(floatingObject)) {
                 floatingObject.setShouldPaint(true);
                 return;
             }
-        } else if (floatingObject.shouldPaint()) {
+        } else {
             floatingObject.setShouldPaint(false);
-            return;
         }
     }
-    // We should have found the ancestor to update shouldPaint flag.
-    ASSERT_NOT_REACHED();
 }
 
 bool LayoutBlockFlow::allowsPaginationStrut() const
 {
     // The block needs to be contained by a LayoutBlockFlow (and not by e.g. a flexbox, grid, or a
     // table (the latter being the case for table cell or table caption)). The reason for this
     // limitation is simply that LayoutBlockFlow child layout code is the only place where we pick
     // up the struts and handle them. We handle floats and regular in-flow children, and that's
     // all. We could handle this in other layout modes as well (and even for out-of-flow children),
     // but currently we don't.
@@ skipping 394 matching lines @@
 
     return LayoutBlock::invalidatePaintIfNeeded(paintInvalidationState);
 }
 
 void LayoutBlockFlow::invalidateDisplayItemClients(PaintInvalidationReason invalidationReason) const
 {
     BlockFlowPaintInvalidator(*this).invalidateDisplayItemClients(invalidationReason);
 }
 
 } // namespace blink