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

third_party/WebKit/Source/core/paint/PaintLayerPainter.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/paint/PaintLayerPainter.h"
 
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/ClipPathClipper.h"
 #include "core/paint/FilterPainter.h"
@@ skipping 253 matching lines @@
 
   bool isSelfPaintingLayer = m_paintLayer.isSelfPaintingLayer();
   bool isPaintingOverlayScrollbars =
       paintFlags & PaintLayerPaintingOverlayScrollbars;
   bool isPaintingScrollingContent =
       paintFlags & PaintLayerPaintingCompositingScrollingPhase;
   bool isPaintingCompositedForeground =
       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;
 
   PaintResult result = FullyPainted;
 
   if (paintFlags & PaintLayerPaintingRootBackgroundOnly &&
       !m_paintLayer.layoutObject()->isLayoutView())
     return result;
 
   if (m_paintLayer.layoutObject()->view()->frame() &&
@@ skipping 805 matching lines @@
 
   PaintLayerPaintingInfo paintingInfo(&m_paintLayer,
                                       LayoutRect(enclosingIntRect(damageRect)),
                                       paintFlags, LayoutSize());
   paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
   m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 }  // namespace blink