Aura overlay scrollbars adjust color for dark backgrounds

third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  * Copyright (C) 2008, 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 385 matching lines @@
     ScrollbarTheme::theme().updateScrollbarOverlayStyle(*scrollbar);
     scrollbar->setNeedsPaintInvalidation(AllParts);
   }
 
   if (Scrollbar* scrollbar = verticalScrollbar()) {
     ScrollbarTheme::theme().updateScrollbarOverlayStyle(*scrollbar);
     scrollbar->setNeedsPaintInvalidation(AllParts);
   }
 }
 
-void ScrollableArea::recalculateScrollbarOverlayStyle(Color backgroundColor) {
-  ScrollbarOverlayStyle oldOverlayStyle = getScrollbarOverlayStyle();
-  ScrollbarOverlayStyle overlayStyle = ScrollbarOverlayStyleDefault;
-
+ScrollbarOverlayStyle ScrollableArea::calculateScrollbarOverlayStyle(
+    Color backgroundColor) {
   // Reduce the background color from RGB to a lightness value
   // and determine which scrollbar style to use based on a lightness
   // heuristic.
   double hue, saturation, lightness;
   backgroundColor.getHSL(hue, saturation, lightness);
   if (lightness <= .5)
-    overlayStyle = ScrollbarOverlayStyleLight;
+    return ScrollbarOverlayStyleLight;
+  return ScrollbarOverlayStyleDark;
+}
+
+void ScrollableArea::recalculateScrollbarOverlayStyle(Color backgroundColor,
+                                                      bool isTransparent) {
+  ScrollbarOverlayStyle oldOverlayStyle = getScrollbarOverlayStyle();
+  ScrollbarOverlayStyle overlayStyle = ScrollbarOverlayStyleDefault;
+
+  // will calc color when paint if it is transparent
+  if (!isTransparent) {
+    overlayStyle = calculateScrollbarOverlayStyle(backgroundColor);
+  }
 
   if (oldOverlayStyle != overlayStyle)
     setScrollbarOverlayStyle(overlayStyle);
 }
 
 void ScrollableArea::setScrollbarNeedsPaintInvalidation(
     ScrollbarOrientation orientation) {
   if (orientation == HorizontalScrollbar) {
     if (GraphicsLayer* graphicsLayer = layerForHorizontalScrollbar()) {
       graphicsLayer->setNeedsDisplay();
@@ skipping 163 matching lines @@
   return IntSize(std::max(0, size.width() - verticalScrollbarWidth()),
                  std::max(0, size.height() - horizontalScrollbarHeight()));
 }
 
 DEFINE_TRACE(ScrollableArea) {
   visitor->trace(m_scrollAnimator);
   visitor->trace(m_programmaticScrollAnimator);
 }
 
 }  // namespace blink