Aura overlay scrollbars adjust color for dark backgrounds

ui/native_theme/native_theme_aura.cc

Index: ui/native_theme/native_theme_aura.cc
diff --git a/ui/native_theme/native_theme_aura.cc b/ui/native_theme/native_theme_aura.cc
index d03a0d3211edc0f216a157fa5ff93b7ce22cab68..8a074cbee44912ab09e65ae6a5c4acd2aabc4d49 100644
--- a/ui/native_theme/native_theme_aura.cc
+++ b/ui/native_theme/native_theme_aura.cc
@@ -35,8 +35,11 @@ constexpr int kOverlayScrollbarMinimumLength = 12;
 constexpr SkAlpha kOverlayScrollbarAlphaNormal = 0x4D;
 constexpr SkAlpha kOverlayScrollbarAlphaHovered = 0x80;
 constexpr SkAlpha kOverlayScrollbarAlphaPressed = 0x80;
-constexpr SkColor kOverlayScrollbarThumbColor = SK_ColorBLACK;
-constexpr SkColor kOverlayScrollbarStrokeColor = SK_ColorWHITE;
+constexpr SkColor kOverlayScrollbarThumbDefaultColor = SK_ColorBLACK;
+constexpr SkColor kOverlayScrollbarThumbLightColor = SK_ColorWHITE;
+constexpr SkColor kOverlayScrollbarStrokeDefaultColor = SK_ColorWHITE;
+constexpr SkColor kOverlayScrollbarStrokeLightColor = SK_ColorBLACK;
+
 
 SkAlpha ThumbAlphaForState(NativeTheme::State state) {
   bool overlay = IsOverlayScrollbarEnabled();
@@ -177,15 +180,18 @@ void NativeThemeAura::PaintScrollbarTrack(
   canvas->drawIRect(gfx::RectToSkIRect(rect), paint);
 }
 
-void NativeThemeAura::PaintScrollbarThumb(SkCanvas* canvas,
-                                          Part part,
-                                          State state,
-                                          const gfx::Rect& rect) const {
+void NativeThemeAura::PaintScrollbarThumb(
+    SkCanvas* canvas,
+    Part part,
+    State state,
+    const gfx::Rect& rect,
+    ScrollbarOverlayColorTheme theme) const {
   // Do not paint if state is disabled.
   if (state == kDisabled)
     return;
 
-  PaintScrollbarThumbStateTransition(canvas, part, state, state, 1.0, rect);
+  PaintScrollbarThumbStateTransition(canvas, part, state, state, 1.0, rect,
+                                     theme);
 }
 
 void NativeThemeAura::PaintScrollbarThumbStateTransition(
@@ -194,18 +200,29 @@ void NativeThemeAura::PaintScrollbarThumbStateTransition(
     State start_state,
     State end_state,
     double progress,
-    const gfx::Rect& rect) const {
+    const gfx::Rect& rect,
+    ScrollbarOverlayColorTheme theme) const {
   TRACE_EVENT0("blink", "NativeThemeAura::PaintScrollbarThumbStateTransition");
   gfx::Rect thumb_rect(rect);
   SkColor thumb_color;
   if (IsOverlayScrollbarEnabled()) {
+    SkColor stroke_color;
+     if (theme == ScrollbarOverlayColorThemeLight) {
+      thumb_color = kOverlayScrollbarThumbLightColor;
+      stroke_color = kOverlayScrollbarStrokeLightColor;
+    } else {
+      thumb_color = kOverlayScrollbarThumbDefaultColor;
+      stroke_color = kOverlayScrollbarStrokeDefaultColor;
+    }
+
     // In overlay mode, draw a stroke (border).
     constexpr int kStrokeWidth = kOverlayScrollbarStrokeWidth;
     SkAlpha stroke_alpha = gfx::Tween::IntValueBetween(
         progress, ThumbAlphaForState(start_state),
         ThumbAlphaForState(end_state));
+
     SkPaint paint;
-    paint.setColor(SkColorSetA(kOverlayScrollbarStrokeColor, stroke_alpha));
+    paint.setColor(SkColorSetA(stroke_color, stroke_alpha));
     paint.setStyle(SkPaint::kStroke_Style);
     paint.setStrokeWidth(kStrokeWidth);
 
@@ -216,7 +233,7 @@ void NativeThemeAura::PaintScrollbarThumbStateTransition(
 
     // Inset the all the edges edges so we fill-in the stroke below.
     thumb_rect.Inset(kStrokeWidth, kStrokeWidth);
-    thumb_color = kOverlayScrollbarThumbColor;
+
   } else {
     // If there are no scrollbuttons then provide some padding so that the thumb
     // doesn't touch the top of the track.