[Views] Allow dialog delegates to use a custom padding for the extra view

ui/views/window/dialog_delegate.cc

Index: ui/views/window/dialog_delegate.cc
diff --git a/ui/views/window/dialog_delegate.cc b/ui/views/window/dialog_delegate.cc
index f2431aa088f89710e756aaf17b5045c788965572..2ce3d34a4fe95d148cb8da60014c935b44a7033d 100644
--- a/ui/views/window/dialog_delegate.cc
+++ b/ui/views/window/dialog_delegate.cc
@@ -77,6 +77,10 @@ View* DialogDelegate::CreateExtraView() {
   return NULL;
 }
 
+bool DialogDelegate::GetExtraViewPadding(int* padding) {
+  return false;
+}
+
 View* DialogDelegate::CreateTitlebarExtraView() {
   return NULL;
 }