Make short-running Git operations synchronous.

sdk/lib/_internal/pub/test/test_pub.dart

Index: sdk/lib/_internal/pub/test/test_pub.dart
diff --git a/sdk/lib/_internal/pub/test/test_pub.dart b/sdk/lib/_internal/pub/test/test_pub.dart
index 2380ed31d10e97c22177401a1f972b7de5a88863..7c8a6a99fc9a521aede09fbcface1483087c8282 100644
--- a/sdk/lib/_internal/pub/test/test_pub.dart
+++ b/sdk/lib/_internal/pub/test/test_pub.dart
@@ -645,13 +645,9 @@ void ensureGit() {
     currentSchedule.timeout = new Duration(seconds: 30);
   }
 
-  schedule(() {
-    return gitlib.isInstalled.then((installed) {
-      if (!installed) {
-        throw new Exception("Git must be installed to run this test.");
-      }
-    });
-  }, 'ensuring that Git is installed');
+  if (!gitlib.isInstalled) {
+    throw new Exception("Git must be installed to run this test.");
+  }
 }
 
 /// Create a lock file for [package] without running `pub get`.