Fix swarming tests not running in parallel

tools-webrtc/mb/mb.py

 #!/usr/bin/env python
 # Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 """MB - the Meta-Build wrapper around GYP and GN
@@ skipping 1069 matching lines @@
           '../../tools-webrtc/valgrind/webrtc_tests.sh',
           '--tool',
           'memcheck',
           '--target',
           'Release',
           '--build-dir',
           '..',
           '--test',
       ]
 
-      gtest_parallel = (test_type != 'non_parallel_console_test_launcher' and
-                        not memcheck)
-      if gtest_parallel:
+      if not memcheck:
         extra_files += [
             '../../third_party/gtest-parallel/gtest-parallel',
             '../../tools-webrtc/gtest-parallel-wrapper.py',
         ]
         sep = '\\' if self.platform == 'win32' else '/'
         output_dir = '${ISOLATED_OUTDIR}' + sep + 'test_logs'
         gtest_parallel_wrapper = [
             '../../tools-webrtc/gtest-parallel-wrapper.py',
             '--output_dir=%s' % output_dir,
         ]
 
       asan = 'is_asan=true' in vals['gn_args']
       msan = 'is_msan=true' in vals['gn_args']
       tsan = 'is_tsan=true' in vals['gn_args']
 
       executable_prefix = '.\\' if self.platform == 'win32' else './'
       executable_suffix = '.exe' if self.platform == 'win32' else ''
       executable = executable_prefix + target + executable_suffix
 
       cmdline = (['../../testing/xvfb.py'] if xvfb else
                  ['../../testing/test_env.py'])
-      if memcheck:
-        cmdline += memcheck_cmdline
-      elif gtest_parallel:
-        cmdline += gtest_parallel_wrapper
-      cmdline += [
-          executable,
+      cmdline += memcheck_cmdline if memcheck else gtest_parallel_wrapper
+      cmdline.append(executable)
+      if test_type == 'non_parallel_console_test_launcher' and not memcheck:
+        # Still use the gtest-parallel-wrapper.py script since we need it to
+        # run tests on swarming, but don't execute tests in parallel.
+        cmdline.append('--workers=1')
+
+      cmdline.extend([
           '--',
           '--asan=%d' % asan,
           '--msan=%d' % msan,
           '--tsan=%d' % tsan,
-      ]
+      ])
 
     cmdline += isolate_map[target].get('args', [])
 
     return cmdline, extra_files
 
   def ToAbsPath(self, build_path, *comps):
     return self.PathJoin(self.src_dir,
                          self.ToSrcRelPath(build_path),
                          *comps)
 
@@ skipping 396 matching lines @@
   # Then check to see if the arg contains any metacharacters other than
   # double quotes; if it does, quote everything (including the double
   # quotes) for safety.
   if any(a in UNSAFE_FOR_CMD for a in arg):
     arg = ''.join('^' + a if a in ALL_META_CHARS else a for a in arg)
   return arg
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))