Add Vector2d classes that represent offsets, instead of using Point.

ui/views/controls/textfield/native_textfield_views.cc

Index: ui/views/controls/textfield/native_textfield_views.cc
diff --git a/ui/views/controls/textfield/native_textfield_views.cc b/ui/views/controls/textfield/native_textfield_views.cc
index 02e4c49cd59d3fb38c1387f70b322845694e5082..28ccdcb16a7e36cb88527f19b455d44fb568e2c0 100644
--- a/ui/views/controls/textfield/native_textfield_views.cc
+++ b/ui/views/controls/textfield/native_textfield_views.cc
@@ -112,8 +112,7 @@ bool NativeTextfieldViews::OnMousePressed(const ui::MouseEvent& event) {
 
 bool NativeTextfieldViews::ExceededDragThresholdFromLastClickLocation(
     const ui::MouseEvent& event) {
-  gfx::Point location_delta = event.location().Subtract(last_click_location_);
-  return ExceededDragThreshold(location_delta.x(), location_delta.y());
+  return ExceededDragThreshold(event.location() - last_click_location_);
 }
 
 bool NativeTextfieldViews::OnMouseDragged(const ui::MouseEvent& event) {