[Telemetry] Allow the Monsoon to power the device under test.

The monsoon provides power for the device, so for devices with no
real battery, we need a chance to turn them on after the monsoon
enables voltage output to the device.

BUG=

Review URL: https://codereview.chromium.org/400863002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285005 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/telemetry/core/backends/chrome/android_browser_finder.py

@@ -18,6 +18,7 @@ from telemetry.core import util
 from telemetry.core.backends import adb_commands
 from telemetry.core.backends.chrome import android_browser_backend
 from telemetry.core.platform import android_platform_backend
+from telemetry.core.platform.profiler import monsoon
 
 
 CHROME_PACKAGE_NAMES = {
@@ -176,6 +177,7 @@ def CanFindAvailableBrowsers(logging=real_logging):
         adb_works = False
   return adb_works
 
+
 def FindAllAvailableBrowsers(finder_options, logging=real_logging):
   """Finds all the desktop browsers available on this machine."""
   if not CanFindAvailableBrowsers(logging=logging):
@@ -183,15 +185,38 @@ def FindAllAvailableBrowsers(finder_options, logging=real_logging):
                  'Will not try searching for Android browsers.')
     return []
 
-  device = None
-  if finder_options.android_device:
-    devices = [finder_options.android_device]
-  else:
-    devices = adb_commands.GetAttachedDevices()
+  def _GetDevices():
+    if finder_options.android_device:
+      return [finder_options.android_device]
+    else:
+      return adb_commands.GetAttachedDevices()
 
-  if len(devices) == 0:
-    logging.info('No android devices found.')
-    return []
+  devices = _GetDevices()
+
+  if not devices:
+    try:
+      m = monsoon.Monsoon(wait=False)
+      m.SetUsbPassthrough(1)
+      m.SetVoltage(3.8)
+      m.SetMaxCurrent(8)
+      logging.warn("""
+Monsoon power monitor detected, but no Android devices.
+
+The Monsoon's power output has been enabled. Please now ensure that:
+
+  1. The Monsoon's front and back USB are connected to the host.
+  2. The Device is connected to the Monsoon's main and USB channels.
+  3. The Device is turned on.
+
+Waiting for device...
+""")
+      util.WaitFor(_GetDevices, 600)
+      devices = _GetDevices()
+      if not devices:
+        raise IOError()
+    except IOError:
+      logging.info('No android devices found.')
+      return []
 
   if len(devices) > 1:
     logging.warn(

tools/telemetry/telemetry/core/platform/power_monitor/monsoon_power_monitor.py

@@ -103,15 +103,16 @@ class MonsoonPowerMonitor(power_monitor.PowerMonitor):
     """
     power_samples = []
     total_energy_consumption_mwh = 0
+
     result = json.loads(powermonitor_output)
-    timedelta_h = result['duration_s'] / len(result['samples']) / 3600
-    for (current_a, voltage_v) in result['samples']:
-      energy_consumption_mw = current_a * voltage_v * 10**3
-      total_energy_consumption_mwh += energy_consumption_mw * timedelta_h
-      power_samples.append(energy_consumption_mw)
-    # -------- Collect and Process Data -------------
+    if result['samples']:
+      timedelta_h = result['duration_s'] / len(result['samples']) / 3600
+      for (current_a, voltage_v) in result['samples']:
+        energy_consumption_mw = current_a * voltage_v * 10**3
+        total_energy_consumption_mwh += energy_consumption_mw * timedelta_h
+        power_samples.append(energy_consumption_mw)
+
     out_dict = {}
-    # Raw power usage samples.
     out_dict['identifier'] = 'monsoon'
     out_dict['power_samples_mw'] = power_samples
     out_dict['energy_consumption_mwh'] = total_energy_consumption_mwh