NodeFrame: Use now()

Author: linbingquan

src/nodes/core/NodeFrame.js

@@ -291,16 +291,22 @@ class NodeFrame {
 
 		this.frameId ++;
 
-		if ( this.lastTime === undefined ) this.lastTime = performance.now();
+		if ( this.lastTime === undefined ) this.lastTime = now();
 
-		this.deltaTime = ( performance.now() - this.lastTime ) / 1000;
+		this.deltaTime = ( now() - this.lastTime ) / 1000;
 
-		this.lastTime = performance.now();
+		this.lastTime = now();
 
 		this.time += this.deltaTime;
 
 	}
 
 }
 
+function now() {
+
+	return performance.now();
+
+}
+
 export default NodeFrame;