Refactor ChooserDialogView to use borders instead of content margins.

ui/views/window/dialog_delegate.h

Index: ui/views/window/dialog_delegate.h
diff --git a/ui/views/window/dialog_delegate.h b/ui/views/window/dialog_delegate.h
index becd06928bf5016689dffffd5dd68ac9c8cb6dcb..054edfe6b212fc81e4850d9fd0bd381489a4cc4e 100644
--- a/ui/views/window/dialog_delegate.h
+++ b/ui/views/window/dialog_delegate.h
@@ -104,12 +104,7 @@ class VIEWS_EXPORT DialogDelegate : public ui::DialogModel,
   ClientView* CreateClientView(Widget* widget) override;
   NonClientFrameView* CreateNonClientFrameView(Widget* widget) override;
 
-  // Create a frame view using the new dialog style.
-  // |content_margins|: margins between the content and the inside of the
-  // border, in pixels.
-  static NonClientFrameView* CreateDialogFrameView(
-      Widget* widget,
-      const gfx::Insets& content_margins);
+  static NonClientFrameView* CreateDialogFrameView(Widget* widget);
 
   // Returns true if this particular dialog should use a Chrome-styled frame
   // like the one used for bubbles. The alternative is a more platform-native