In LabelButton::SetIsDefault: ~ is bitwise NOT, not !.

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 9fab63b0086236b3ee021f5a2c3762cfdc8e75a6..7abdc3b3ae857e558816571d42edd866a4f864bf 100644
--- a/ui/views/controls/button/label_button.cc
+++ b/ui/views/controls/button/label_button.cc
@@ -128,7 +128,7 @@ void LabelButton::SetIsDefault(bool is_default) {
   // STYLE_BUTTON uses bold text to indicate default buttons.
   if (style_ == STYLE_BUTTON) {
     int style = label_->font().GetStyle();
-    style = is_default ? style | gfx::Font::BOLD : style & !gfx::Font::BOLD;
+    style = is_default ? style | gfx::Font::BOLD : style & ~gfx::Font::BOLD;
     label_->SetFont(label_->font().DeriveFont(0, style));
   }
 }