[MD] simplify and unify some ink drop center calculations

chrome/browser/ui/views/toolbar/back_button.cc

Index: chrome/browser/ui/views/toolbar/back_button.cc
diff --git a/chrome/browser/ui/views/toolbar/back_button.cc b/chrome/browser/ui/views/toolbar/back_button.cc
index 05618a96abd011d8a8c4c6c8d5f76caef9e8c1a3..6e99ded8144fe1dfb5bdc3d607ea4f558552b4e0 100644
--- a/chrome/browser/ui/views/toolbar/back_button.cc
+++ b/chrome/browser/ui/views/toolbar/back_button.cc
@@ -29,14 +29,6 @@ void BackButton::SetLeadingMargin(int margin) {
   InvalidateLayout();
 }
 
-gfx::Point BackButton::GetInkDropCenter() const {
-  int visible_width = GetPreferredSize().width();
-  return gfx::Point(
-      GetMirroredXWithWidthInView(margin_leading_, visible_width) +
-          visible_width / 2,
-      height() / 2);
-}
-
 const char* BackButton::GetClassName() const {
   return "BackButton";
 }