#2361. Improve some flaky tests on Web (#2364)

diff --git a/LibTest/async/Future/Future.delayed_A01_t02.dart b/LibTest/async/Future/Future.delayed_A01_t02.dart
index 3a22b3c..06b7255 100644
--- a/LibTest/async/Future/Future.delayed_A01_t02.dart
+++ b/LibTest/async/Future/Future.delayed_A01_t02.dart
@@ -22,7 +22,7 @@
     ? Duration(milliseconds: 40)
     : Duration.zero;
 
-check(delayms, value) {
+check(delayms) {
   Duration delay = durationInMilliseconds(delayms);
   Stopwatch sw = new Stopwatch();
   asyncStart();
@@ -36,7 +36,9 @@
 }
 
 main() {
-  check(0, 11);
-  check(300, 3);
-  check(50, 22);
+  check(0);
+  check(30);
+  check(50);
+  check(100);
+  check(150);
 }
diff --git a/LibTest/async/Stream/Stream.periodic_A01_t01.dart b/LibTest/async/Stream/Stream.periodic_A01_t01.dart
index 97a351b..061eed4 100644
--- a/LibTest/async/Stream/Stream.periodic_A01_t01.dart
+++ b/LibTest/async/Stream/Stream.periodic_A01_t01.dart
@@ -50,5 +50,7 @@
   check(1);
   check(10);
   check(30);
+  check(50);
   check(100);
+  check(200);
 }
diff --git a/LibTest/async/Timer/Timer_A01_t01.dart b/LibTest/async/Timer/Timer_A01_t01.dart
index 311fae7..2590591 100644
--- a/LibTest/async/Timer/Timer_A01_t01.dart
+++ b/LibTest/async/Timer/Timer_A01_t01.dart
@@ -35,10 +35,14 @@
 }
 
 main() {
+  check(150);
+  check(100);
+  check(50);
   check(25);
   check(10);
   check(2);
   check(1);
   check(0);
   check(-5);
+  check(-50);
 }
diff --git a/LibTest/html/Element/onMouseOver_A01_t01.dart b/LibTest/html/Element/onMouseOver_A01_t01.dart
index 119b2cd..f3419e2 100644
--- a/LibTest/html/Element/onMouseOver_A01_t01.dart
+++ b/LibTest/html/Element/onMouseOver_A01_t01.dart
@@ -20,6 +20,7 @@
       Expect.equals(type, e.type);
       if (!fired) {
         asyncEnd();
+        fired = true;
       }
     });
     var event = new MouseEvent(type);