Make short-running Git operations synchronous.

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

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Test infrastructure for testing pub. Unlike typical unit tests, most pub
 /// tests are integration tests that stage some stuff on the file system, run
 /// pub, and then validate the results. This library provides an API to build
 /// tests like that.
 library test_pub;
 
@@ skipping 627 matching lines @@
 /// validation gives an easier-to-understand error when that requirement isn't
 /// met than just failing in the middle of a test when pub invokes git.
 ///
 /// This also increases the [Schedule] timeout to 30 seconds on Windows,
 /// where Git runs really slowly.
 void ensureGit() {
   if (Platform.operatingSystem == "windows") {
     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`.
 ///
 /// [sandbox] is a list of path dependencies to be found in the sandbox
 /// directory. [pkg] is a list of packages in the Dart repo's "pkg" directory;
 /// each package listed here and all its dependencies will be linked to the
 /// version in the Dart repo.
 ///
 /// [hosted] is a list of package names to version strings for dependencies on
@@ skipping 243 matching lines @@
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     return description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }
 
 /// A [StreamMatcher] that matches multiple lines of output.
 StreamMatcher emitsLines(String output) => inOrder(output.split("\n"));