views: support vertical-drag-to-end on textfields

ui/views/style/platform_style.h

Index: ui/views/style/platform_style.h
diff --git a/ui/views/style/platform_style.h b/ui/views/style/platform_style.h
index e6916176bf4de6958f2518b8231de018547dd145..97f697e4fd4e2f2e4e9e41137453c1b8601fbaca 100644
--- a/ui/views/style/platform_style.h
+++ b/ui/views/style/platform_style.h
@@ -34,6 +34,10 @@ class VIEWS_EXPORT PlatformStyle {
   // Whether dialog-default buttons are given a bold font style.
   static const bool kDefaultLabelButtonHasBoldFont;
 
+  // Whether dragging vertically above or below a textfield's bounds selects to
+  // the left or right end of the text from the cursor, respectively.
+  static const bool kTextfieldDragVerticallyDragsToEnd;
+
   // Creates an ImageSkia containing the image to use for the combobox arrow.
   // The |is_enabled| argument is true if the control the arrow is for is
   // enabled, and false if the control is disabled. The |style| argument is the