views::LabelButton should not call virtual methods from its constructor

ui/views/controls/button/custom_button_unittest.cc

Index: ui/views/controls/button/custom_button_unittest.cc
diff --git a/ui/views/controls/button/custom_button_unittest.cc b/ui/views/controls/button/custom_button_unittest.cc
index de3be98fe5541c63730f7c00a7ab67cf52cfcee3..c632aca170e4b2c8d24dc9e9cc0e10178471d5f0 100644
--- a/ui/views/controls/button/custom_button_unittest.cc
+++ b/ui/views/controls/button/custom_button_unittest.cc
@@ -215,7 +215,8 @@ TEST_F(CustomButtonTest, GestureEventsSetState) {
 TEST_F(CustomButtonTest, AsCustomButton) {
   base::string16 text;
 
-  LabelButton label_button(NULL, text);
+  LabelButton label_button(nullptr);
+  label_button.Init(text);
   EXPECT_TRUE(CustomButton::AsCustomButton(&label_button));
 
   ImageButton image_button(NULL);