Additional flakiness reducing changes. Also rerun DRT on false positive tests.

tools/testing/dart/test_runner.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.
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
@@ skipping 144 matching lines @@
  * [TestCase] this is the output of.
  */
 class TestOutput {
   TestCase testCase;
   int exitCode;
   bool timedOut;
   bool failed = false;
   List<String> stdout;
   List<String> stderr;
   Duration time;
+  /** 
+   * Set to true if we encounter a condition in the output that indicates we 
+   * need to rerun this test. 
+   */
+  bool requestRetry;
 
   TestOutput(this.testCase, this.exitCode, this.timedOut, this.stdout,
              this.stderr, this.time) {
     testCase.output = this;
+    requestRetry = false;
   }
 
   String get result() =>
       hasCrashed ? CRASH : (hasTimedOut ? TIMEOUT : (hasFailed ? FAIL : PASS));
 
   bool get unexpectedOutput() => !testCase.expectedOutcomes.contains(result);
 
   bool get hasCrashed() {
     if (new Platform().operatingSystem() == 'windows') {
       // The VM uses std::abort to terminate on asserts.
@@ skipping 23 matching lines @@
       }
       previous_line = line;
     }
 
     // If the browser test failed, it may have been because DumpRenderTree
     // and the virtual framebuffer X server didn't hook up.
     for (String line in stderr) {
       if (line.contains('Gtk-WARNING **: cannot open display: :99')) {
         // If we get the X server error, return the expected value
         // We cannot restart the test from here.  Issue dart:1135 is filed.
-        return testCase.isNegative;
+        requestRetry = true;
+        return true;
       }
     }
     return true;
   }
 
   // Reverse result of a negative test.
   bool get hasFailed() => (testCase.isNegative ? !didFail : didFail);
 }
 
 /**
@@ skipping 17 matching lines @@
   List<Function> handlers;
 
   RunningProcess(TestCase this.testCase);
 
   void exitHandler(int exitCode) {
     new TestOutput(testCase, exitCode, timedOut, stdout,
                    stderr, new Date.now().difference(startTime));
     process.close();
     timeoutTimer.cancel();
     if (testCase.output.unexpectedOutput && testCase.configuration['verbose']) {
-      print(testCase.output.stdout);
-      print(testCase.output.stderr);
+      print(testCase.displayName);
+      for (var line in testCase.output.stderr) {
+        print(line);
+      }
+      for (var line in testCase.output.stdout) {
+        print(line);
+      }
     }
     if (testCase is BrowserTestCase && testCase.output.unexpectedOutput &&
         !testCase.isRerun) {
       // Selenium tests can be flaky. Try rerunning.
+      testCase.output.requestRetry = true;
+    }
+    if (testCase.output.requestRetry) {
+      testCase.output.requestRetry = false;
+      this.timedOut = false;
       testCase.isRerun = true;
-      this.timedOut = false;
+      print("Potential flake. Re-running " + testCase.displayName);
       this.start();
     } else {
       testCase.completed();
     }
   }
 
   void compilerExitHandler(int exitCode) {
     if (exitCode != 0) {
       stderr.add('test.dart: Compilation step failed (exit code $exitCode)\n');
       exitHandler(exitCode);
@@ skipping 361 matching lines @@
           test.displayName != 'dartc/junit_tests') {
         _ensureDartcBatchRunnersStarted(test.executablePath);
         _getDartcBatchRunnerProcess().startTest(test);
       } else {
         new RunningProcess(test).start();
       }
       _numProcesses++;
     }
   }
 }