Take desktop screenshots after test failures in test_runner.py.

ios/build/bots/scripts/test_runner.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Test runners for iOS."""
 
 import argparse
 import collections
 import errno
 import os
@@ skipping 270 matching lines @@
     else:
       parser = gtest_utils.GTestLogParser()
 
     proc = subprocess.Popen(
         cmd,
         env=self.get_launch_env(),
         stdout=subprocess.PIPE,
         stderr=subprocess.STDOUT,
     )
 
+    failure_count = 0
     while True:
       line = proc.stdout.readline()
       if not line:
         break
       line = line.rstrip()
       parser.ProcessLine(line)
       print line
       sys.stdout.flush()
 
+      # If there is a new test failure, take a desktop screenshot.
+      # parser.FailedTests() considers in progress tests as failed, so a check
+      # is needed that the current test isn't included in the list of failed
+      # tests.
+      new_failure_count = len([test for test in parser.FailedTests()
+                               if test != parser.GetCurrentTest()])
+      if (new_failure_count > failure_count):
+        self.screenshot_desktop()
+        failure_count = new_failure_count
+
     proc.wait()
     sys.stdout.flush()
 
     for test in parser.FailedTests(include_flaky=True):
       # Test cases are named as <test group>.<test case>. If the test case
       # is prefixed with "FLAKY_", it should be reported as flaked not failed.
       if '.' in test and test.split('.', 1)[1].startswith('FLAKY_'):
         result.flaked_tests[test] = parser.FailureDescription(test)
       else:
         result.failed_tests[test] = parser.FailureDescription(test)
@@ skipping 450 matching lines @@
     """
     env = super(DeviceTestRunner, self).get_launch_env()
     if self.xctest_path:
       env['NSUnbufferedIO'] = 'YES'
       # e.g. ios_web_shell_egtests
       env['APP_TARGET_NAME'] = os.path.splitext(
           os.path.basename(self.app_path))[0]
       # e.g. ios_web_shell_egtests_module
       env['TEST_TARGET_NAME'] = env['APP_TARGET_NAME'] + '_module'
     return env