Add new method to disable android device charging.

build/android/pylib/device/device_utils_test.py

Index: build/android/pylib/device/device_utils_test.py
diff --git a/build/android/pylib/device/device_utils_test.py b/build/android/pylib/device/device_utils_test.py
index b7e807e06d74cf063d247e10b99c93fe870b4b5c..2457e1737e4b927890ec4f6ce233e1b936b19ea0 100755
--- a/build/android/pylib/device/device_utils_test.py
+++ b/build/android/pylib/device/device_utils_test.py
@@ -1467,6 +1467,31 @@ class DeviceUtilsSetChargingTest(DeviceUtilsTest):
         (self.call.device.GetCharging(), False)):
       self.device.SetCharging(False)
 
+  def testSetChargingDefault_enabled(self):
+    with self.assertCalls(
+      (self.call.device.FileExists(mock.ANY), False),
+      (self.call.device.FileExists(mock.ANY), False),
+      (self.call.device.RunShellCommand(mock.ANY, check_return=True), []),
+      (self.call.device.GetCharging(), False),
+      (self.call.device.RunShellCommand(mock.ANY, check_return=True), []),
+      (self.call.device.GetCharging(), True)):
+        self.device.SetCharging(True)
+        self.assertEqual(
+            'dumpsys battery reset',
+            self.device._cache['charging_config']['enable_command'])
+
+  def testSetChargingDefault_disabled(self):
+    with self.assertCalls(
+      (self.call.device.FileExists(mock.ANY), False),
+      (self.call.device.FileExists(mock.ANY), False),
+      (self.call.device.RunShellCommand(mock.ANY, check_return=True), []),
+      (self.call.device.GetCharging(), True),
+      (self.call.device.RunShellCommand(mock.ANY, check_return=True), []),
+      (self.call.device.GetCharging(), False)):
+        self.device.SetCharging(False)
+        self.assertEqual(
+            'dumpsys battery set usb 0',
+            self.device._cache['charging_config']['disable_command'])
 
 
 class DeviceUtilsStrTest(DeviceUtilsTest):