[Mac] Redesign the avatar bubble UI

ui/native_theme/native_theme_win.cc

Index: ui/native_theme/native_theme_win.cc
diff --git a/ui/native_theme/native_theme_win.cc b/ui/native_theme/native_theme_win.cc
index a09be6c30e74669915ba344663dfa945d381e572..55c9f486a37efca1977bede426c688f5e8534e94 100644
--- a/ui/native_theme/native_theme_win.cc
+++ b/ui/native_theme/native_theme_win.cc
@@ -50,6 +50,7 @@ const SkColor kUnfocusedBorderColor = SkColorSetRGB(0xd9, 0xd9, 0xd9);
 const SkColor kButtonBackgroundColor = SkColorSetRGB(0xde, 0xde, 0xde);
 const SkColor kButtonHighlightColor = SkColorSetARGB(200, 255, 255, 255);
 const SkColor kButtonHoverColor = SkColorSetRGB(6, 45, 117);
+const SkColor kButtonHoverBackgroundColor = SkColorSetRGB(0xEA, 0xEA, 0xEA);
 // MenuItem:
 const SkColor kEnabledMenuItemForegroundColor = SkColorSetRGB(6, 45, 117);
 const SkColor kDisabledMenuItemForegroundColor = SkColorSetRGB(161, 161, 146);
@@ -532,6 +533,8 @@ SkColor NativeThemeWin::GetSystemColor(ColorId color_id) const {
       return kButtonHighlightColor;
     case kColorId_ButtonHoverColor:
       return kButtonHoverColor;
+    case kColorId_ButtonHoverBackgroundColor:
+      return kButtonHoverBackgroundColor;
 
     // MenuItem
     case kColorId_EnabledMenuItemForegroundColor: