[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..100eef4ab54710feff86bd5f9aa49a8fc96c9e1c 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):
@@ -58,7 +76,7 @@ class _TestCollection(object):
         if self._tests_in_progress == 0:
           return None
         try:
-          return self._tests.pop()
+          return self._tests.pop(0)
         except IndexError:
           # Another thread beat us to the avaliable test, wait again.
           self._item_avaliable_or_all_done.clear()
@@ -114,7 +132,7 @@ def _RunTestsFromQueue(runner, test_collection, out_results):
       if retry and test.tries <= 3:
         # Retry non-passing results, only record passing results.
         out_results.append(test_result.TestResults.FromRun(ok=result.ok))
-        logging.warning('****Retrying test, try #%s.' % test.tries)
+        logging.warning('****Will retry test, try #%s.' % test.tries)
         test_collection.add(_Test(test=retry, tries=test.tries))
       else:
         # All tests passed or retry limit reached. Either way, record results.
@@ -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'.