Change Aura overlay scrollbars from solid color to painted scrollbars.

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

Index: third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp
index 655c9203cf97f5ad111eb4dff98f233ba3baa4db..38911f5eddd312dbf290508bcf3572e177141dea 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp
@@ -130,8 +130,12 @@ PartPaintingParams buttonPartPaintingParams(
 
 ScrollbarTheme& ScrollbarTheme::nativeTheme() {
   if (RuntimeEnabledFeatures::overlayScrollbarsEnabled()) {
+    int thickness = Platform::current()
+                        ->themeEngine()
+                        ->getSize(WebThemeEngine::PartScrollbarVerticalThumb)
+                        .width;
     DEFINE_STATIC_LOCAL(ScrollbarThemeOverlay, theme,
-                        (10, 0, ScrollbarThemeOverlay::AllowHitTest));
+                        (thickness, 0, ScrollbarThemeOverlay::AllowHitTest));
     return theme;
   }