Added isFlushing.

Author: mitar

src/core/global-api/index.js

@@ -18,7 +18,7 @@ import {
 } from '../util/index'
 
 import Dep, { pushTarget, popTarget } from '../observer/dep'
-import { afterFlush, forceFlush } from '../observer/scheduler'
+import { afterFlush, forceFlush, isFlushing } from '../observer/scheduler'
 import Watcher from '../observer/watcher'
 
 export function initGlobalAPI (Vue: GlobalAPI) {
@@ -51,6 +51,7 @@ export function initGlobalAPI (Vue: GlobalAPI) {
     popTarget,
     afterFlush,
     forceFlush,
+    isFlushing,
     Watcher
   }
 

src/core/observer/scheduler.js

@@ -212,6 +212,13 @@ export function forceFlush (maxUpdateCount?: number) {
   flushSchedulerQueue(maxUpdateCount)
 }
 
+/**
+ * Are we inside a flush?
+ */
+export function isFlushing () {
+  return flushing;
+}
+
 /**
  * Used in watchers to wrap provided getters to set scheduler flags.
  */