Update CrOS logout button for MD.

ui/views/controls/button/label_button.cc

Index: ui/views/controls/button/label_button.cc
diff --git a/ui/views/controls/button/label_button.cc b/ui/views/controls/button/label_button.cc
index 53b92479495add0133a42dfd94401d93bb5ebb8c..9812efc27c6bae3e391017b191952e838485c7b5 100644
--- a/ui/views/controls/button/label_button.cc
+++ b/ui/views/controls/button/label_button.cc
@@ -192,6 +192,10 @@ void LabelButton::SetFontList(const gfx::FontList& font_list) {
   label_->SetFontList(cached_normal_font_list_);
 }
 
+void LabelButton::AdjustFontSize(int font_size_delta) {
+  LabelButton::SetFontList(GetFontList().DeriveWithSizeDelta(font_size_delta));
+}
+
 void LabelButton::SetElideBehavior(gfx::ElideBehavior elide_behavior) {
   label_->SetElideBehavior(elide_behavior);
 }