Support for pixel layout tests.

utils/testrunner/pipeline_task.dart

 // Copyright (c) 2012, 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.
 
 /**
  * A test execution pipeline is made up of a list of tasks. Each task is a
  * subclass of [PipelineTask].
  */
 abstract class PipelineTask {
 
-  abstract void execute(Path testfile, List stdout, List stderr,
+  abstract execute(Path testfile, List stdout, List stderr,
                        bool logging, Function exitHandler);
 
   void cleanup(Path testfile, List stdout, List stderr,
                bool verboseLogging, bool keepTestFiles) {
   }
 
   void deleteFiles(List templates, Path testfile, bool logging, bool keepFiles,
                    List stdout) {
     if (!keepFiles) {
       for (var template in templates) {
         var fname = expandMacros(template, testfile);
-        deleteFile(fname);
-        if (logging) {
-          stdout.add('Removing $fname');
+        if (deleteFile(fname)) {
+          if (logging) {
+            stdout.add('Removed $fname');
+          }
+        } else {
+          if (logging) {
+            stdout.add('Failed to remove $fname');
+          }
         }
       }
     }
   }
 
   String flattenPath(String path) {
     return makePathAbsolute(path).
         replaceAll(Platform.pathSeparator, "_").
         replaceAll(":","");
   }
 
   // This takes a string used in a template and does macro expansion for
   // a specific test file.
   String expandMacros(String template, Path testfile) {
     String path = makePathAbsolute(testfile.directoryPath.toString());
     return template.
         replaceAll(Macros.fullFilePath, testfile.toNativePath()).
         replaceAll(Macros.filenameNoExtension,
             testfile.filenameWithoutExtension).
         replaceAll(Macros.filename, testfile.filename).
         replaceAll(Macros.directory, path).
         replaceAll(Macros.flattenedDirectory, flattenPath(path));
   }
 }