Fix scrollbars on the edit bookmarks window and task manager under Windows classic theme.

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 eb108a9780600ba7eda2fc4b49a2c898f901b5e5..5b43b29681720e4b11d667e874e7acbdfe73db03 100644
--- a/ui/native_theme/native_theme_win.cc
+++ b/ui/native_theme/native_theme_win.cc
@@ -254,6 +254,17 @@ gfx::Size NativeThemeWin::GetPartSize(Part part,
         size.cx = 13;
         size.cy = 13;
         break;
+      case kScrollbarDownArrow:
+      case kScrollbarLeftArrow:
+      case kScrollbarRightArrow:
+      case kScrollbarUpArrow:
+      case kScrollbarHorizontalThumb:
+      case kScrollbarVerticalThumb:
+      case kScrollbarHorizontalTrack:
+      case kScrollbarVerticalTrack:
+        size.cx = size.cy = GetSystemMetrics(SM_CXVSCROLL) /
+            ui::win::GetDeviceScaleFactor();
+        break;
       default:
         size.cx = 0;
         size.cy = 0;