refactor CCScene

* use member initializer list
* add const to member function

cocos/2d/CCScene.cpp

@@ -52,28 +52,28 @@ THE SOFTWARE.
 NS_CC_BEGIN
 
 Scene::Scene()
-{
+: _defaultCamera(Camera::create())
+, _cameraOrderDirty(true)
+, _event(Director::getInstance()->getEventDispatcher()->addCustomEventListener(Director::EVENT_PROJECTION_CHANGED, std::bind(&Scene::onProjectionChanged, this, std::placeholders::_1)))
+#if CC_USE_PHYSICS
+, _physicsWorld(nullptr)
+#endif
 #if CC_USE_3D_PHYSICS && CC_ENABLE_BULLET_INTEGRATION
-    _physics3DWorld = nullptr;
-    _physics3dDebugCamera = nullptr;
+, _physics3DWorld(nullptr)
+, _physics3dDebugCamera(nullptr)
 #endif
 #if CC_USE_NAVMESH
-    _navMesh = nullptr;
-    _navMeshDebugCamera = nullptr;
-#endif
-#if CC_USE_PHYSICS
-    _physicsWorld = nullptr;
+, _navMesh(nullptr)
+, _navMeshDebugCamera(nullptr)
 #endif
+{
     _ignoreAnchorPointForPosition = true;
     setAnchorPoint(Vec2(0.5f, 0.5f));
 
-    _cameraOrderDirty = true;
-
     //create default camera
-    _defaultCamera = Camera::create();
+
     addChild(_defaultCamera);
 
-    _event = Director::getInstance()->getEventDispatcher()->addCustomEventListener(Director::EVENT_PROJECTION_CHANGED, std::bind(&Scene::onProjectionChanged, this, std::placeholders::_1));
     _event->retain();
 
     Camera::_visitingCamera = nullptr;

cocos/2d/CCScene.h

@@ -180,7 +180,7 @@ class CC_DLL Scene : public Node
      * @return The 3d physics world of the scene.
      * @js NA
      */
-    Physics3DWorld* getPhysics3DWorld() { return _physics3DWorld; }
+    Physics3DWorld* getPhysics3DWorld() const { return _physics3DWorld; }
 
     /** 
      * Set Physics3D debug draw camera.