Aura overlay scrollbars adjust color for dark backgrounds

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 951 matching lines @@
   // overlay style might need to be changed to have contrast against the
   // background.
   Color oldBackground;
   if (oldStyle) {
     oldBackground = oldStyle->visitedDependentColor(CSSPropertyBackgroundColor);
   }
   Color newBackground =
       box().style()->visitedDependentColor(CSSPropertyBackgroundColor);
 
   if (newBackground != oldBackground) {
-    recalculateScrollbarOverlayStyle(newBackground);
+    recalculateScrollbarOverlayStyle(newBackground, m_layer.isTransparent());
   }
 }
 
 bool PaintLayerScrollableArea::updateAfterCompositingChange() {
   layer()->updateScrollingStateAfterCompositingChange();
   const bool layersChanged = m_topmostScrollChild != m_nextTopmostScrollChild;
   m_topmostScrollChild = m_nextTopmostScrollChild;
   m_nextTopmostScrollChild = nullptr;
   return layersChanged;
 }
@@ skipping 283 matching lines @@
           LayoutScrollbarPart::createAnonymous(&box().document(), this);
       m_scrollCorner->setDangerousOneWayParent(&box());
     }
     m_scrollCorner->setStyleWithWritingModeOfParent(corner.release());
   } else if (m_scrollCorner) {
     m_scrollCorner->destroy();
     m_scrollCorner = nullptr;
   }
 }
 
+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) {
   if (!hasScrollbar() && !box().canResize())
     return false;
 
   IntRect resizeControlRect;
   if (box().style()->resize() != RESIZE_NONE) {
     resizeControlRect =
         resizerCornerRect(box().pixelSnappedBorderBoxRect(), ResizerForPointer);
@@ skipping 692 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetsAfterLayout();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink