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 aadab753778f42c2baff9892774d049ea66e2da3..33249f530511cd13314015391c29b3a02c4a6118 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -246,6 +246,8 @@ PaintLayerPainter::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.
@@ -254,11 +256,14 @@ PaintLayerPainter::PaintResult PaintLayerPainter::paintLayerContents(
   // 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'.
+  //
+  // The outline needs to be painted in the decoration phase rather than the
+  // background phase.
   bool shouldPaintSelfOutline =
       isSelfPaintingLayer && !isPaintingOverlayScrollbars &&
-      ((isPaintingScrollingContent && isPaintingCompositedBackground) ||
-       (!isPaintingScrollingContent && isPaintingCompositedForeground)) &&
+      (isPaintingCompositedDecoration || !isPaintingScrollingContent) &&
       m_paintLayer.layoutObject()->styleRef().hasOutline();
+
   bool shouldPaintContent = m_paintLayer.hasVisibleContent() &&
                             isSelfPaintingLayer && !isPaintingOverlayScrollbars;