Fix the absence of padding on some UI buttons.

ui/views/layout/layout_constants.h

Index: ui/views/layout/layout_constants.h
diff --git a/ui/views/layout/layout_constants.h b/ui/views/layout/layout_constants.h
index e375ad7f08be10ed9f54751cd8e9899d034221da..620a28de6c6df48df58cb81d4c5c538b53f10c37 100644
--- a/ui/views/layout/layout_constants.h
+++ b/ui/views/layout/layout_constants.h
@@ -83,6 +83,12 @@ constexpr int kCheckboxIndent = 10;
 // and the start of its corresponding text.
 constexpr int kItemLabelSpacing = 10;
 
+// Padding on the left and right of a button's contents.
+const int kButtonHorizontalPadding = 16;
+
+// Default minimum width of buttons.
+const int kMinimumButtonWidth = 48;
+
 // Minimum width of dialog buttons.
 const int kDialogMinimumButtonWidth = 75;