Aura overlay scrollbars adjust color for dark backgrounds

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 9767274a2a6a1a2784f48e208702e6774aae7ad4..f5c9506e7b1f4fd7c1df4e0136dfd35e5504aa5e 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -969,7 +969,7 @@ void PaintLayerScrollableArea::updateAfterStyleChange(
       box().style()->visitedDependentColor(CSSPropertyBackgroundColor);
 
   if (newBackground != oldBackground) {
-    recalculateScrollbarOverlayStyle(newBackground);
+    recalculateScrollbarOverlayStyle(newBackground, m_layer.isTransparent());
   }
 }
 
@@ -1273,6 +1273,25 @@ void PaintLayerScrollableArea::updateScrollCornerStyle() {
   }
 }
 
+ScrollbarOverlayStyle PaintLayerScrollableArea::getScrollbarOverlayStyle()
+    const {
+  ScrollbarOverlayStyle style = ScrollableArea::getScrollbarOverlayStyle();
+
+  if (style == ScrollbarOverlayStyleDefault) {

[bokan, 2016/10/18 19:55:25]

ScrollableArea has a layoutBox() method that returns the LayoutBox for the
ScrollableArea. You should be able to use that to implement
getScrollbarOverlayStyle once in ScrollableArea rather than separately for
PaintLayerScrollableArea and FrameView.

+    PaintLayer* layer = &this->m_layer;
+    while (layer->isTransparent() && layer->parent())
+      layer = layer->parent();
+
+    if (layer->layoutBox() && layer->layoutBox()->style()) {
+      Color color = layer->layoutBox()->style()->visitedDependentColor(
+          CSSPropertyBackgroundColor);
+      style = calculateScrollbarOverlayStyle(color);
+    }
+  }
+
+  return style;
+}
+
 bool PaintLayerScrollableArea::hitTestOverflowControls(
     HitTestResult& result,
     const IntPoint& localPoint) {