Removed hard-coded color values from scrollbar overlay.

Removed hard-coded color references for the overlay scrollbar and
added the relevant color ids. Added appropriate selectors for gtk
native theme.

Bug: 1003612
Change-Id: I5c7a8354a151249e2fc5e2a52244c441a15979fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1950861Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#722516}

chrome/browser/ui/libgtkui/native_theme_gtk.cc

@@ -174,6 +174,12 @@ SkColor SkColorFromColorId(ui::NativeTheme::ColorId color_id) {
       return SkColorSetRGB(0x00, 0x00, 0xEE);
     }
 
+    // Scrollbar
+    case ui::NativeTheme::kColorId_OverlayScrollbarThumbBackground:
+      return GetBgColor("#GtkScrollbar#scrollbar #trough");
+    case ui::NativeTheme::kColorId_OverlayScrollbarThumbForeground:
+      return GetBgColor("#GtkScrollbar#scrollbar #slider");
+
     // Separator
     case ui::NativeTheme::kColorId_SeparatorColor:
       return GetSeparatorColor("GtkSeparator#separator.horizontal");

ui/native_theme/common_theme.cc

@@ -13,6 +13,7 @@
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/skia_util.h"
+#include "ui/native_theme/overlay_scrollbar_constants_aura.h"
 
 namespace ui {
 
@@ -282,6 +283,14 @@ SkColor GetAuraColor(NativeTheme::ColorId color_id,
     case NativeTheme::kColorId_LinkPressed:
       return gfx::kGoogleBlue600;
 
+    // Scrollbar
+    case NativeTheme::kColorId_OverlayScrollbarThumbBackground:
+      return SK_ColorBLACK;
+    case NativeTheme::kColorId_OverlayScrollbarThumbForeground:
+      return SkColorSetA(SK_ColorWHITE, (kOverlayScrollbarStrokeNormalAlpha /
+                                         kOverlayScrollbarThumbNormalAlpha) *
+                                            SK_AlphaOPAQUE);
+
     // Separator
     case NativeTheme::kColorId_SeparatorColor:
       return gfx::kGoogleGrey300;

ui/native_theme/native_theme.h

@@ -356,6 +356,8 @@ class NATIVE_THEME_EXPORT NativeTheme {
     kColorId_LinkDisabled,
     kColorId_LinkEnabled,
     kColorId_LinkPressed,
+    kColorId_OverlayScrollbarThumbBackground,
+    kColorId_OverlayScrollbarThumbForeground,
     // Separator
     kColorId_SeparatorColor,
     // TabbedPane

ui/views/controls/scrollbar/overlay_scroll_bar.cc

@@ -60,7 +60,8 @@ gfx::Size OverlayScrollBar::Thumb::CalculatePreferredSize() const {
 void OverlayScrollBar::Thumb::OnPaint(gfx::Canvas* canvas) {
   cc::PaintFlags fill_flags;
   fill_flags.setStyle(cc::PaintFlags::kFill_Style);
-  fill_flags.setColor(SK_ColorBLACK);
+  fill_flags.setColor(GetNativeTheme()->GetSystemColor(
+      ui::NativeTheme::kColorId_OverlayScrollbarThumbBackground));
   gfx::RectF fill_bounds(GetLocalBounds());
   fill_bounds.Inset(gfx::InsetsF(IsHorizontal() ? kThumbHoverOffset : 0,
                                  IsHorizontal() ? 0 : kThumbHoverOffset, 0, 0));
@@ -71,10 +72,8 @@ void OverlayScrollBar::Thumb::OnPaint(gfx::Canvas* canvas) {
 
   cc::PaintFlags stroke_flags;
   stroke_flags.setStyle(cc::PaintFlags::kStroke_Style);
-  stroke_flags.setColor(
-      SkColorSetA(SK_ColorWHITE, (ui::kOverlayScrollbarStrokeNormalAlpha /
-                                  ui::kOverlayScrollbarThumbNormalAlpha) *
-                                     SK_AlphaOPAQUE));
+  stroke_flags.setColor(GetNativeTheme()->GetSystemColor(
+      ui::NativeTheme::kColorId_OverlayScrollbarThumbForeground));
   stroke_flags.setStrokeWidth(kThumbStrokeVisualSize);
   stroke_flags.setStrokeCap(cc::PaintFlags::kSquare_Cap);