Fix overflow:overlay scrollbar width for paint.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 8a5fd7f3bc135dc51d8b1fe6a2e3615ff0f209be..1aade931fb874877763a65fd831f9f19b24ef804 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -504,7 +504,10 @@ IntSize PaintLayerScrollableArea::maximumScrollOffsetInt() const {
 
   IntSize contentSize = contentsSize();
   IntSize visibleSize =
-      pixelSnappedIntRect(box().overflowClipRect(box().location())).size();
+      pixelSnappedIntRect(
+          box().overflowClipRect(box().location(),
+                                 IgnorePlatformAndCSSOverlayScrollbarSize))
+          .size();
 
   FrameHost* host = layoutBox()->document().frameHost();
   DCHECK(host);
@@ -1296,9 +1299,13 @@ int PaintLayerScrollableArea::verticalScrollbarWidth(
     OverlayScrollbarClipBehavior overlayScrollbarClipBehavior) const {
   if (!hasVerticalScrollbar())
     return 0;
-  if ((verticalScrollbar()->isOverlayScrollbar() ||
-       box().style()->overflowY() == EOverflow::kOverlay) &&
-      (overlayScrollbarClipBehavior == IgnoreOverlayScrollbarSize ||
+  if (box().style()->overflowY() == EOverflow::kOverlay &&
+      overlayScrollbarClipBehavior ==
+          IgnorePlatformAndCSSOverlayScrollbarSize) {
+    return 0;
+  }
+  if (verticalScrollbar()->isOverlayScrollbar() &&
+      (overlayScrollbarClipBehavior == IgnorePlatformOverlayScrollbarSize ||

[skobes, 2017/03/07 19:28:07]

Don't you need to check for IgnorePlatformAndCSSOverlayScrollbarSize in this
branch too?

[szager1, 2017/03/07 19:44:38]

Whoops!  Fixed.

        !verticalScrollbar()->shouldParticipateInHitTesting())) {
     return 0;
   }
@@ -1309,9 +1316,13 @@ int PaintLayerScrollableArea::horizontalScrollbarHeight(
     OverlayScrollbarClipBehavior overlayScrollbarClipBehavior) const {
   if (!hasHorizontalScrollbar())
     return 0;
-  if ((horizontalScrollbar()->isOverlayScrollbar() ||
-       box().style()->overflowX() == EOverflow::kOverlay) &&
-      (overlayScrollbarClipBehavior == IgnoreOverlayScrollbarSize ||
+  if (overlayScrollbarClipBehavior ==
+          IgnorePlatformAndCSSOverlayScrollbarSize &&
+      box().style()->overflowX() == EOverflow::kOverlay) {
+    return 0;
+  }
+  if (horizontalScrollbar()->isOverlayScrollbar() &&
+      (overlayScrollbarClipBehavior == IgnorePlatformOverlayScrollbarSize ||
        !horizontalScrollbar()->shouldParticipateInHitTesting())) {
     return 0;
   }