[Telemetry] Small fixes in android_app_backend

This CL includes two fixes:
- Ensure the app was not running after trying to launch.
- Be more specific when matching process names for the app.

These were split off from:
https://codereview.chromium.org/1510833002/

BUG=

Review URL: https://codereview.chromium.org/1606243002

Cr-Commit-Position: refs/heads/master@{#370704}

tools/telemetry/telemetry/internal/backends/android_app_backend.py

@@ -46,8 +46,11 @@ class AndroidAppBackend(app_backend.AppBackend):
     # TODO(slamm): check if the wait for "ps" check is really needed, or
     # whether the "blocking=True" fall back is sufficient.
     has_ready_predicate = self._is_app_ready_predicate is not None
-    self.device.StartActivity(self._start_intent,
-                              blocking=not has_ready_predicate)
+    self.device.StartActivity(
+        self._start_intent,
+        blocking=not has_ready_predicate,
+        force_stop=True,  # Ensure app was not running.
+    )
     if has_ready_predicate:
       util.WaitFor(is_app_ready, timeout=60)
 
@@ -87,7 +90,9 @@ class AndroidAppBackend(app_backend.AppBackend):
 
   def GetProcesses(self, process_filter=None):
     if process_filter is None:
-      process_filter = lambda n: re.match('^' + self._default_process_name, n)
+      # Match process names of the form: 'process_name[:subprocess]'.
+      process_filter = re.compile(
+          '^%s(:|$)' % re.escape(self._default_process_name)).match
 
     processes = set()
     ps_output = self.platform_backend.GetPsOutput(['pid', 'name'])

tools/telemetry/telemetry/internal/backends/android_app_backend_unittest.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.
+import collections
+import mock
+import unittest
+
+from telemetry.internal.backends import android_app_backend
+from devil.android.sdk import intent as intent_module
+
+
+_FakeAndroidProcess = collections.namedtuple(
+    'AndroidProcess', ['app_backend', 'pid', 'name'])
+
+
+class AndroidAppBackendUnittest(unittest.TestCase):
+
+  def setUp(self):
+    self.platform_backend = mock.Mock()
+    self.start_intent = intent_module.Intent(
+        package='com.example.my_app',
+        activity='com.example.my_app.LaunchMyApp')
+    self.app_backend = android_app_backend.AndroidAppBackend(
+        self.platform_backend, self.start_intent)
+
+  @mock.patch('telemetry.internal.backends.android_app_backend'
+              '.android_process.AndroidProcess', _FakeAndroidProcess)
+  def testGetProcesses(self):
+    # Only processes belonging to 'com.example.my_app' should match.
+    self.platform_backend.GetPsOutput.return_value = [
+      ['1111', 'com.example.my_app'],
+      ['2222', 'com.example.my_appointments_helper'],
+      ['3333', 'com.example.my_app:service'],
+      ['4444', 'com.example.some_other_app'],
+      ['5555', 'com_example_my_app'],
+    ]
+    process_pids = set(p.pid for p in self.app_backend.GetProcesses())
+    self.assertEquals(process_pids, set(['1111', '3333']))