Add new method to disable android device charging.

build/android/pylib/device/device_utils.py

Index: build/android/pylib/device/device_utils.py
diff --git a/build/android/pylib/device/device_utils.py b/build/android/pylib/device/device_utils.py
index b6fd7323bb9a3c71e566049719a963bba2ce9023..b34c0bcd14cb887759a35650428459f05fdf1c4f 100644
--- a/build/android/pylib/device/device_utils.py
+++ b/build/android/pylib/device/device_utils.py
@@ -69,6 +69,7 @@ _CONTROL_CHARGING_COMMANDS = [
   },
 ]
 
+_DUMPSYS_BATTERY_DISABLED = '  (UPDATES STOPPED -- use \'reset\' to restart)'
 
 @decorators.WithExplicitTimeoutAndRetries(
     _DEFAULT_TIMEOUT, _DEFAULT_RETRIES)
@@ -1414,8 +1415,13 @@ class DeviceUtils(object):
     # Skip the first line, which is just a header.
     for line in self.RunShellCommand(
         ['dumpsys', 'battery'], check_return=True)[1:]:
-      k, v = line.split(': ', 1)
-      result[k.strip()] = v.strip()
+      # If usb charging has been disabled, an extra line of header exists.
+      if line != _DUMPSYS_BATTERY_DISABLED:

[jbudorick, 2015/03/09 21:49:55]

If this line appears, is it the only thing printed? Will we see valid dumpsys
information alongside this message?

If this is the only thing printed, we should handle this differently.

Also, exact text contents is liable to change between Android versions. This
could flake if someone decides to make minor style changes to the line (e.g.
switch to a 4 space indent). Can we change what we're looking for to account for
things like that?

[rnephew (Wrong account), 2015/03/09 23:58:09]

The output looks like this:
Current Battery Service state:
  (UPDATES STOPPED -- use 'reset' to restart)
  AC powered: false
  USB powered: false
  Wireless powered: false
  status: 5
  health: 2
  present: true
  level: 100
  scale: 100
  voltage: 4317
  temperature: 269
  technology: Li-ion
I can change it to a regular expression, or just have it skip lines that do not
fit the label: value paradigm.

[jbudorick, 2015/03/10 00:04:43]

Interesting, that's not what I expected.

I don't think we should silently skip. I think we should handle three
possibilities:
  - the line contains "UPDATES STOPPED": log a warning, as you had here before
  - the line fits the key: value paradigm, in which case we handle it as we are
currently
  - neither, in which case we log a warning about an unrecognized line in the
dumpsys output.

[rnephew (Wrong account), 2015/03/10 14:56:35]

Done.

+        k, v = line.split(': ', 1)
+        result[k.strip()] = v.strip()
+      else:
+        logging.warning('Dumpsys battery not recieving updates. '
+                        'Run dumpsys battery reset if this is in error')
     return result
 
   @decorators.WithTimeoutAndRetriesFromInstance()
@@ -1436,6 +1442,28 @@ class DeviceUtils(object):
     return False
 
   @decorators.WithTimeoutAndRetriesFromInstance()
+  def SoftSetCharging(self, enabled, timeout=None, retries=None):

[jbudorick, 2015/03/09 21:49:55]

I don't think this should be separate from SetCharging. I think that we should
always to this in SetCharging _and_ do the specific commands for N4/N5 if we're
handling one of those devices.

Also, whatever you add or change in here should be tested in
device_utils_test.py.

[rnephew (Wrong account), 2015/03/09 23:58:09]

Done.

+    """Enables or disables charging for dumpsys. Device still will
+    silently be charging. Allows for power data collection through dumpsys.
+
+    Args:
+      enabled: A boolean indicating whether charging should be enabled or
+        disabled.
+      timeout: timeout in seconds
+      retries: number of retries
+    """
+    if enabled:
+      command = 'dumpsys battery reset'
+    else:
+      command = 'dumpsys battery set usb 0'
+
+    def set_and_verify_charging():
+      self.RunShellCommand(command, check_return=True)
+      return self.GetCharging() == enabled
+
+    timeout_retry.WaitFor(set_and_verify_charging, wait_period=1)
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
   def SetCharging(self, enabled, timeout=None, retries=None):
     """Enables or disables charging on the device.