Enables hot-tracking for overflow extension buttons in the app menu

ui/native_theme/native_theme.cc

Index: ui/native_theme/native_theme.cc
diff --git a/ui/native_theme/native_theme.cc b/ui/native_theme/native_theme.cc
index f15f144b8c08746c03a6f56855e65a64b5d73c61..96b0072ce706ec0501d83581adfef4b2fd164de3 100644
--- a/ui/native_theme/native_theme.cc
+++ b/ui/native_theme/native_theme.cc
@@ -4,10 +4,16 @@
 
 #include "ui/native_theme/native_theme.h"
 
+#include <cstring>
+
 #include "ui/native_theme/native_theme_observer.h"
 
 namespace ui {
 
+NativeTheme::ExtraParams::ExtraParams() {
+  memset(this, 0, sizeof(*this));
+}
+
 void NativeTheme::SetScrollbarColors(unsigned inactive_color,
                                      unsigned active_color,
                                      unsigned track_color) {