Fix force stop using wrong "ps" cmd.

devil/devil/android/device_utils_test.py

Index: devil/devil/android/device_utils_test.py
diff --git a/devil/devil/android/device_utils_test.py b/devil/devil/android/device_utils_test.py
index 2490209631075502df03c9f81c035b8da05ef2b6..80157a964217d2e6e4f5827dcf253f7a1a8438a4 100755
--- a/devil/devil/android/device_utils_test.py
+++ b/devil/devil/android/device_utils_test.py
@@ -1539,11 +1539,27 @@ class DeviceUtilsGoHomeTest(DeviceUtilsTest):
 class DeviceUtilsForceStopTest(DeviceUtilsTest):
 
   def testForceStop(self):
-    with self.assertCall(
-        self.call.adb.Shell('p=test.package;if [[ "$(ps)" = *$p* ]]; then '
-                            'am force-stop $p; fi'),
-        ''):
-      self.device.ForceStop('test.package')
+    with self.patch_call(self.call.device.build_version_sdk,
+                     return_value=(version_codes.NOUGAT_MR1)):
+      with self.patch_call(self.call.device.build_id,
+                       return_value='NNN99N'):
+        with self.assertCall(
+            self.call.adb.Shell('p=test.package;if [[ "$(ps)" = *$p* ]]; then '
+                                'am force-stop $p; fi'),
+            ''):
+          self.device.ForceStop('test.package')
+
+  def testForceStop_sdkGreaterThanNougatMR1(self):
+    with self.patch_call(self.call.device.build_version_sdk,
+                     return_value=(version_codes.NOUGAT_MR1 + 1)):
+      with self.patch_call(self.call.device.build_id,
+                       return_value='ZZZ99Z'):
+        with self.assertCall(
+            self.call.adb.Shell(
+                'p=test.package;if [[ "$(ps -e)" = *$p* ]]; then '
+                'am force-stop $p; fi'),
+                ''):
+          self.device.ForceStop('test.package')
 
 
 class DeviceUtilsClearApplicationStateTest(DeviceUtilsTest):