Merge pull request cocos2d#9758 from andyque/update-changelog

Update releasenote

docs/RELEASE_NOTES.md

@@ -148,4 +148,27 @@ camera->enableFrustumCulling(true, true);
 
 Note that when you can make sure that all the stuff is inside the frustum you can turn off the frustum culling.
 
-For more infomation please reffer to the cpptests/CameraTest
+For more infomation please reffer to the cpptests/CameraTest
+
+### Use less resources to create  ui::CheckBox and ui::Slider 
+
+Now we could use less resources to create  ui::CheckBox and ui::Slider.
+
+To create an ui::CheckBox, we could simply pass the normal state box and active texture.
+
+```cpp
+CheckBox* checkBox2 = CheckBox::create("cocosui/check_box_normal.png",
+                                              "cocosui/check_box_active.png");
+```
+
+To create an ui::Slider, we could only pass the slider bar texture and normal ball texture.
+
+```cpp
+Slider* sliderScale9 = Slider::create("cocosui/slidbar.png", "cocosui/sliderballnormal.png");
+```
+
+If the selected state texture is missing, when user press the widget, the normal texture will scale.
+
+If the disable state texture is missing, when the widget is in disable state, we use gray shader to turn the normal state texture to gray.
+
+The original ui::Button also support the gray shader enhancement.