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/LayoutInline.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/ClipPathClipper.h"
@@ skipping 228 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 used to be painted in either the foreground phase or the background

[flackr, 2016/10/25 21:26:30]

No need to mention where it used to be painted, we can just say The outline is
painted as part of the decoration phase which paints content that is not
scrolled and should be above scrolled content.

[yigu, 2016/10/27 20:21:26]

Done.

+  // phase. Now it is painted in the decoration phase.
   bool shouldPaintSelfOutline =
       isSelfPaintingLayer && !isPaintingOverlayScrollbars &&
-      ((isPaintingScrollingContent && isPaintingCompositedBackground) ||
-       (!isPaintingScrollingContent && isPaintingCompositedForeground)) &&
+      (isPaintingCompositedDecoration || !isPaintingScrollingContent) &&
       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 799 matching lines @@
 
   PaintLayerPaintingInfo paintingInfo(&m_paintLayer,
                                       LayoutRect(enclosingIntRect(damageRect)),
                                       paintFlags, LayoutSize());
   paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
   m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 }  // namespace blink