Move test.dart's check for missing test directories from co19 to general framework.

tools/testing/dart/test_suite.dart

Index: tools/testing/dart/test_suite.dart
diff --git a/tools/testing/dart/test_suite.dart b/tools/testing/dart/test_suite.dart
index b6eb454ae9a4976d39a81e46fde0a0263f1c0e84..8728ac7ece6760de6643cda1ed0751472c620a0b 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -224,6 +224,13 @@ class StandardTestSuite implements TestSuite {
   void processDirectory() {
     directoryPath = '$dartDir/$directoryPath';
     Directory dir = new Directory(directoryPath);
+    if (!dir.existsSync()) {

[Mads Ager (google), 2012/02/02 14:33:05]

Since you really want this to be async why not use the async api?

+      print('Directory containing tests not found: $directoryPath');
+      // All paths through test enumeration must be asynchronous.
+      new Timer((ignored){ directoryListingDone(false); }, 0);
+      return;
+    }
+      
     dir.errorHandler = (s) {
       throw s;
     };