[Android] Switch instrumentation tests to the new shard/runner paradigm.

build/android/pylib/base/shard.py

Index: build/android/pylib/base/shard.py
diff --git a/build/android/pylib/base/shard.py b/build/android/pylib/base/shard.py
index fdca5249a06b06f920d7b9ccf7a4d9e9fe026c60..8f9f46e7747953342d1e758d0962880530dff626 100644
--- a/build/android/pylib/base/shard.py
+++ b/build/android/pylib/base/shard.py
@@ -14,6 +14,24 @@ from pylib.utils import reraiser_thread
 import test_result
 
 
+class _ThreadSafeCounter(object):
+  """A threadsafe counter."""
+  def __init__(self):
+    self._lock = threading.Lock()
+    self._value = 0
+
+  def GetAndIncrement(self):
+    """Get the current value and increment it atomically.
+
+    Returns:
+      The value before incrementing.
+    """
+    with self._lock:
+      pre_increment = self._value
+      self._value += 1
+      return pre_increment
+
+
 class _Test(object):
   """Holds a test with additional metadata."""
   def __init__(self, test, tries=0):
@@ -135,24 +153,27 @@ def _RunTestsFromQueue(runner, test_collection, out_results):
       test_collection.test_completed()
 
 
-def _SetUp(runner_factory, device, out_runners):
+def _SetUp(runner_factory, device, out_runners, threadsafe_counter):
   """Creates a test runner for each device and calls SetUp() in parallel.
 
   Note: if a device is unresponsive the corresponding TestRunner will not be
     added to out_runners.
 
   Args:
-    runner_factory: callable that takes a device and returns a TestRunner.
+    runner_factory: callable that takes a device and index and returns a
+      TestRunner object.
     device: the device serial number to set up.
     out_runners: list to add the successfully set up TestRunner object.
+    threadsafe_counter: a _ThreadSafeCounter object used to get shard indices.
   """
   try:
-    logging.warning('*****Creating shard for %s.', device)
-    runner = runner_factory(device)
+    index = threadsafe_counter.GetAndIncrement()
+    logging.warning('*****Creating shard %s for device %s.', index, device)
+    runner = runner_factory(device, index)
     runner.SetUp()
     out_runners.append(runner)
   except android_commands.errors.DeviceUnresponsiveError as e:
-    logging.warning('****Failed to create shard for %s: [%s]', (device, e))
+    logging.warning('****Failed to create shard for %s: [%s]', device, e)
 
 
 def _RunAllTests(runners, tests):
@@ -183,20 +204,23 @@ def _CreateRunners(runner_factory, devices):
     included in the returned list.
 
   Args:
-    runner_factory: callable that takes a device and returns a TestRunner.
+    runner_factory: callable that takes a device and index and returns a
+      TestRunner object.
     devices: list of device serial numbers as strings.
 
   Returns:
     A list of TestRunner objects.
   """
   logging.warning('****Creating %s test runners.' % len(devices))
-  test_runners = []
+  runners = []
+  counter = _ThreadSafeCounter()
   threads = reraiser_thread.ReraiserThreadGroup(
-      [reraiser_thread.ReraiserThread(_SetUp, [runner_factory, d, test_runners])
+      [reraiser_thread.ReraiserThread(_SetUp, [runner_factory, d, runners,
+                                               counter])
        for d in devices])
   threads.StartAll()
   threads.JoinAll()
-  return test_runners
+  return runners
 
 
 def _TearDownRunners(runners):
@@ -215,7 +239,8 @@ def ShardAndRunTests(runner_factory, devices, tests, build_type='Debug'):
   """Run all tests on attached devices, retrying tests that don't pass.
 
   Args:
-    runner_factory: callable that takes a device and returns a TestRunner.
+    runner_factory: callable that takes a device and index and returns a
+      TestRunner object.
     devices: list of attached device serial numbers as strings.
     tests: list of tests to run.
     build_type: either 'Debug' or 'Release'.