Name retained preference write helpers

src/legacy_canvas_view_services.cpp

@@ -46,7 +46,7 @@ public:
         }
 
         app_.canvas->set_density(plan.density);
-        save_legacy_float_preference("vp-scale", plan.density);
+        save_legacy_canvas_viewport_density(plan.density);
     }
 
     void set_cursor_mode(const pp::app::CanvasViewCursorModePlan& plan) override
@@ -57,8 +57,7 @@ public:
 
         const auto mode = static_cast<int>(plan.mode);
         app_.canvas->set_cursor_visibility(static_cast<NodeCanvas::kCursorVisibility>(mode));
-        set_legacy_integer_preference("show-cursor", mode);
-        save_legacy_preferences();
+        save_legacy_canvas_cursor_mode(mode);
     }
 
 private: