Fix overflow:overlay scrollbar width for paint.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 488 matching lines @@
 IntSize PaintLayerScrollableArea::minimumScrollOffsetInt() const {
   return toIntSize(-scrollOrigin());
 }
 
 IntSize PaintLayerScrollableArea::maximumScrollOffsetInt() const {
   if (!box().hasOverflowClip())
     return toIntSize(-scrollOrigin());
 
   IntSize contentSize = contentsSize();
   IntSize visibleSize =
-      pixelSnappedIntRect(box().overflowClipRect(box().location())).size();
+      pixelSnappedIntRect(
+          box().overflowClipRect(box().location(),
+                                 IgnorePlatformAndCSSOverlayScrollbarSize))
+          .size();
 
   Page* page = layoutBox()->document().page();
   DCHECK(page);
   TopDocumentRootScrollerController& controller =
       page->globalRootScrollerController();
 
   // The global root scroller should be clipped by the top FrameView rather
   // than it's overflow clipping box. This is to ensure that content exposed by
   // hiding the URL bar at the bottom of the screen is visible.
   if (this == controller.rootScrollerArea())
@@ skipping 773 matching lines @@
   // Force an update since we know the scrollbars have changed things.
   if (box().document().hasAnnotatedRegions())
     box().document().setAnnotatedRegionsDirty(true);
   return true;
 }
 
 int PaintLayerScrollableArea::verticalScrollbarWidth(
     OverlayScrollbarClipBehavior overlayScrollbarClipBehavior) const {
   if (!hasVerticalScrollbar())
     return 0;
-  if ((verticalScrollbar()->isOverlayScrollbar() ||
-       box().style()->overflowY() == EOverflow::kOverlay) &&
-      (overlayScrollbarClipBehavior == IgnoreOverlayScrollbarSize ||
-       !verticalScrollbar()->shouldParticipateInHitTesting())) {
+  if (overlayScrollbarClipBehavior ==
+          IgnorePlatformAndCSSOverlayScrollbarSize &&
+      box().style()->overflowY() == EOverflow::kOverlay) {
+    return 0;
+  }
+  if ((overlayScrollbarClipBehavior == IgnorePlatformOverlayScrollbarSize ||
+       overlayScrollbarClipBehavior ==
+           IgnorePlatformAndCSSOverlayScrollbarSize ||
+       !verticalScrollbar()->shouldParticipateInHitTesting()) &&
+      verticalScrollbar()->isOverlayScrollbar()) {
     return 0;
   }
   return verticalScrollbar()->scrollbarThickness();
 }
 
 int PaintLayerScrollableArea::horizontalScrollbarHeight(
     OverlayScrollbarClipBehavior overlayScrollbarClipBehavior) const {
   if (!hasHorizontalScrollbar())
     return 0;
-  if ((horizontalScrollbar()->isOverlayScrollbar() ||
-       box().style()->overflowX() == EOverflow::kOverlay) &&
-      (overlayScrollbarClipBehavior == IgnoreOverlayScrollbarSize ||
-       !horizontalScrollbar()->shouldParticipateInHitTesting())) {
+  if (overlayScrollbarClipBehavior ==
+          IgnorePlatformAndCSSOverlayScrollbarSize &&
+      box().style()->overflowX() == EOverflow::kOverlay) {
+    return 0;
+  }
+  if ((overlayScrollbarClipBehavior == IgnorePlatformOverlayScrollbarSize ||
+       overlayScrollbarClipBehavior ==
+           IgnorePlatformAndCSSOverlayScrollbarSize ||
+       !horizontalScrollbar()->shouldParticipateInHitTesting()) &&
+      horizontalScrollbar()->isOverlayScrollbar()) {
     return 0;
   }
   return horizontalScrollbar()->scrollbarThickness();
 }
 
 void PaintLayerScrollableArea::positionOverflowControls() {
   if (!hasScrollbar() && !box().canResize())
     return;
 
   const IntRect borderBox = box().pixelSnappedBorderBoxRect();
@@ skipping 804 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetAfterOverflowChange();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink