always use uid when calling performance.mark (fix #5209)

Author: yyx990803

src/core/instance/init.js

@@ -14,14 +14,18 @@ let uid = 0
 
 export function initMixin (Vue: Class<Component>) {
   Vue.prototype._init = function (options?: Object) {
+    const vm: Component = this
+    // a uid
+    vm._uid = uid++
+
     /* istanbul ignore if */
+    let startTag, endTag
     if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
-      mark('vue-perf-init')
+      startTag = `vue-perf-init:${vm._uid}`
+      endTag = `vue-perf-end:${vm._uid}`
+      mark(startTag)
     }
 
-    const vm: Component = this
-    // a uid
-    vm._uid = uid++
     // a flag to avoid this being observed
     vm._isVue = true
     // merge options
@@ -57,8 +61,8 @@ export function initMixin (Vue: Class<Component>) {
     /* istanbul ignore if */
     if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
       vm._name = formatComponentName(vm, false)
-      mark('vue-perf-init-end')
-      measure(`${vm._name} init`, 'vue-perf-init', 'vue-perf-init-end')
+      mark(endTag)
+      measure(`${vm._name} init`, startTag, endTag)
     }
 
     if (vm.$options.el) {