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pkg/observe/lib/src/microtask.dart

Index: pkg/observe/lib/src/microtask.dart
diff --git a/pkg/observe/lib/src/microtask.dart b/pkg/observe/lib/src/microtask.dart
index e56fb623d6385b76ce5f785899e202b90d80624d..e821973d52a9f7fccb5848ebe683147af069bd29 100644
--- a/pkg/observe/lib/src/microtask.dart
+++ b/pkg/observe/lib/src/microtask.dart
@@ -11,6 +11,7 @@
 library observe.src.microtask;
 
 import 'dart:async' show Completer, runZonedExperimental;
+import 'dart:collection';
 import 'package:observe/observe.dart' show Observable;
 
 // TODO(jmesserly): remove "microtask" from these names and instead import
@@ -27,11 +28,10 @@ import 'package:observe/observe.dart' show Observable;
 void performMicrotaskCheckpoint() {
   Observable.dirtyCheck();
 
-  while (_pending.length > 0) {
-    var pending = _pending;
-    _pending = [];
+  while (_pending.isNotEmpty) {
 
-    for (var callback in pending) {
+    for (int len = _pending.length; len > 0 && _pending.isNotEmpty; len--) {
+      final callback = _pending.removeFirst();
       try {
         callback();
       } catch (e, s) {
@@ -43,17 +43,21 @@ void performMicrotaskCheckpoint() {
   }
 }
 
-List<Function> _pending = [];
+final Queue<Function> _pending = new Queue<Function>();
 
 /**
- * Wraps the [testCase] in a zone that supports [performMicrotaskCheckpoint],
+ * Wraps the [body] in a zone that supports [performMicrotaskCheckpoint],
  * and returns the test case.
  */
-wrapMicrotask(void testCase()) {
+// TODO(jmesserly): do we want to support nested microtasks similar to nested
+// zones? Instead of a single pending list we'd need one per wrapMicrotask,
+// and [performMicrotaskCheckpoint] would only run pending callbacks
+// corresponding to the innermost wrapMicrotask body.
+wrapMicrotask(void body()) {
   return () {
     runZonedExperimental(() {
       try {
-        testCase();
+        body();
       } finally {
         performMicrotaskCheckpoint();
       }