Don't apply clips to children of composited-scrolling elements for overlap testing.

third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp

 // 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.
 
 #include "core/layout/compositing/CompositingInputsUpdater.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutView.h"
@@ skipping 130 matching lines @@
           ->setNeedsGraphicsLayerUpdate(GraphicsLayerUpdateSubtree);
     updateType = ForceUpdate;
   }
 
   if (updateType == ForceUpdate) {
     PaintLayer::AncestorDependentCompositingInputs properties;
     PaintLayer::RareAncestorDependentCompositingInputs rareProperties;
 
     if (!layer->isRootLayer()) {
       if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
-        properties.clippedAbsoluteBoundingBox =
+        properties.unclippedAbsoluteBoundingBox =
             enclosingIntRect(m_geometryMap.absoluteRect(
                 FloatRect(layer->boundingBoxForCompositingOverlapTest())));
         // FIXME: Setting the absBounds to 1x1 instead of 0x0 makes very little
         // sense, but removing this code will make JSGameBench sad.
         // See https://codereview.chromium.org/13912020/
-        if (properties.clippedAbsoluteBoundingBox.isEmpty())
-          properties.clippedAbsoluteBoundingBox.setSize(IntSize(1, 1));
+        if (properties.unclippedAbsoluteBoundingBox.isEmpty())
+          properties.unclippedAbsoluteBoundingBox.setSize(IntSize(1, 1));
 
         IntRect clipRect =
             pixelSnappedIntRect(layer->clipper()
                                     .backgroundClipRect(ClipRectsContext(
                                         m_rootLayer, AbsoluteClipRects))
                                     .rect());
+        properties.clippedAbsoluteBoundingBox =
+            properties.unclippedAbsoluteBoundingBox;
         properties.clippedAbsoluteBoundingBox.intersect(clipRect);
       }
 
       const PaintLayer* parent = layer->parent();
       rareProperties.opacityAncestor =
           parent->isTransparent() ? parent : parent->opacityAncestor();
       rareProperties.transformAncestor =
           parent->transform() ? parent : parent->transformAncestor();
       rareProperties.filterAncestor = parent->hasFilterInducingProperty()
                                           ? parent
@@ skipping 101 matching lines @@
   ASSERT(!layer->needsCompositingInputsUpdate());
 
   for (PaintLayer* child = layer->firstChild(); child;
        child = child->nextSibling())
     assertNeedsCompositingInputsUpdateBitsCleared(child);
 }
 
 #endif
 
 }  // namespace blink