Have Chrome draw top window border when using custom titlebar.

chrome/browser/themes/theme_properties.h

Index: chrome/browser/themes/theme_properties.h
diff --git a/chrome/browser/themes/theme_properties.h b/chrome/browser/themes/theme_properties.h
index 7bc6709d6e05582e0d40b9bc826333387d68da42..4161e6dbbc0efc1deb0a7cd590c3ea4eddcbc283 100644
--- a/chrome/browser/themes/theme_properties.h
+++ b/chrome/browser/themes/theme_properties.h
@@ -155,6 +155,11 @@ class ThemeProperties {
     GRADIENT_TOOLBAR_BUTTON_PRESSED,
     GRADIENT_TOOLBAR_BUTTON_PRESSED_INACTIVE,
 #endif  // OS_MACOSX
+
+#if defined(OS_WIN)
+    // The color of the 1px border around the window on Windows 10.
+    COLOR_ACCENT_BORDER,
+#endif  // OS_WIN
   };
 
   // Used by the browser theme pack to parse alignments from something like