Fix analyzer warnings in tools/testing/dart/test_progress.dart

tools/testing/dart/test_progress.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.
 
 library test_progress;
 
 import "dart:async";
 import "dart:io";
 import "dart:io" as io;
 import "dart:convert" show JSON;
@@ skipping 301 matching lines @@
           .openWrite(mode: FileMode.APPEND);
     }
     _sink.write("${JSON.encode(record)}\n");
   }
 }
 
 class UnexpectedCrashDumpArchiver extends EventListener {
   final archivedBinaries = new Set<String>();
 
   void done(TestCase test) {
-    if (test.unexpectedOutput && test.result == Expectation.CRASH) {
+    if (test.unexpectedOutput &&
+        test.result == Expectation.CRASH &&
+        test.lastCommandExecuted is ProcessCommand) {
       final name = "core.${test.lastCommandOutput.pid}";
       final file = new File(name);
       final exists = file.existsSync();
       if (exists) {
+        final lastCommand = test.lastCommandExecuted as ProcessCommand;
         // We have a coredump for the process. This coredump will be archived by
         // CoreDumpArchiver (see tools/utils.py). For debugging purposes we
         // need to archive the crashed binary as well. To simplify the
         // archiving code we simply copy binaries into current folder next to
         // core dumps and name them `core.${mode}_${arch}_${binary_name}`.
-        final binName = test.lastCommandExecuted.executable;
+        final binName = lastCommand.executable;
         final binFile = new File(binName);
         final binBaseName = new Path(binName).filename;
         if (archivedBinaries.contains(binBaseName)) {
           return;
         }
 
         if (binFile.existsSync()) {
           final mode = test.configuration['mode'];
           final arch = test.configuration['arch'];
           TestUtils.copyFile(new Path(binName),
@@ skipping 354 matching lines @@
       return new VerboseProgressIndicator(startTime);
     case 'status':
       return new ProgressIndicator(startTime);
     case 'buildbot':
       return new BuildbotProgressIndicator(startTime);
     default:
       assert(false);
       return null;
   }
 }