Initial support to test.dart for running precompiler tests on android devices

tools/test.dart

Index: tools/test.dart
diff --git a/tools/test.dart b/tools/test.dart
index bbfdf258cfedc62378168386c7bea12fdf7aa3cd..e00357d956c316bc20d7d65aa4d385fe45eecb47 100755
--- a/tools/test.dart
+++ b/tools/test.dart
@@ -61,6 +61,9 @@ void main(List<String> arguments) {
     var optionsParser = new TestOptionsParser();
     var configurations = optionsParser.parse(arguments);
     if (configurations != null && configurations.length > 0) {
+      // All the testing is carried out asynchronously in tasks created by this
+      // call.
+      // TODO(26372): Ensure that all tasks complete before the returned future.
       testConfigurations(configurations);
     }
   });