Object Mutation with Locker Service enabled

lockerMutationReproTest.cmp

<aura:component implements="flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes" access="global" >
    <aura:attribute name="lockedObj" type="Object" />
    <aura:handler name="init" value="{!this}" action="{!c.doInit}" />
    <button onclick="{!c.addAtributeViaMutation}">Add Attribute via mutation then simple set</button>
    <button onclick="{!c.addAtributeDeepSet}">Add Attribute via deep set</button>
    <button onclick="{!c.log}">Log</button>
	<div>Existing Attribute: {!v.lockedObj.existingAttribute}</div>
	<div>New Attribute via mutation: {!v.lockedObj.newAttribute}</div>
	<div>New Attribute via deep set: {!v.lockedObj.newAttributeDeep}</div>
</aura:component>

lockerMutationReproTestController.js

({
    doInit : function(component, event, helper){
        var initialObject = {existingAttribute: 'Existing'};
        component.set('v.lockedObj',initialObject);  
    },
    addAtributeViaMutation : function(component, event, helper){
        var obj = component.get('v.lockedObj');
        obj.newAttribute = 'New';
        component.set('v.lockedObj',obj);
    },
    addAtributeDeepSet : function(component, event, helper) {
        component.set('v.lockedObj.newAttributeDeep', 'New');
        component.set('v.lockedObj.wat', 'wat???');
    },
    log : function(component, event, helper){
        console.log(component.get('v.lockedObj'));
    }
})