Fix the bug that negative outline-offset is covered up by composited

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

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index e1c8fdce368965828ee0faf852f8e417f6fe30fb..00a8002542c586d033085e37a5ee937d2674e5ae 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -271,19 +271,18 @@ PaintResult PaintLayerPainter::paintLayerContents(
       paintFlags & PaintLayerPaintingCompositingForegroundPhase;
   bool isPaintingCompositedBackground =
       paintFlags & PaintLayerPaintingCompositingBackgroundPhase;
+  bool isPaintingCompositedDecoration =
+      paintFlags & PaintLayerPaintingCompositingDecorationPhase;
   bool isPaintingOverflowContents =
       paintFlags & PaintLayerPaintingOverflowContents;
   // Outline always needs to be painted even if we have no visible content.
-  // Also, the outline is painted in the background phase during composited
-  // scrolling.  If it were painted in the foreground phase, it would move with
-  // the scrolled content. When not composited scrolling, the outline is painted
-  // in the foreground phase. Since scrolled contents are moved by paint
-  // invalidation in this case, the outline won't get 'dragged along'.
+  // It is painted as part of the decoration phase which paints content that
+  // is not scrolled and should be above scrolled content.
   bool shouldPaintSelfOutline =
       isSelfPaintingLayer && !isPaintingOverlayScrollbars &&
-      ((isPaintingScrollingContent && isPaintingCompositedBackground) ||
-       (!isPaintingScrollingContent && isPaintingCompositedForeground)) &&
+      (isPaintingCompositedDecoration || !isPaintingScrollingContent) &&

[chrishtr, 2016/11/17 21:15:57]

What about cases when there is composited scrolling but no decoration layer?

[chrishtr, 2016/11/17 22:40:21]

Ah, now I see. Thanks for explaining.

[yigu, 2016/11/18 04:14:07]

In the cases we don't create decoration layer, the decoration phase is still
there regardless.

       m_paintLayer.layoutObject()->styleRef().hasOutline();
+
   bool shouldPaintContent = m_paintLayer.hasVisibleContent() &&
                             isSelfPaintingLayer && !isPaintingOverlayScrollbars;