Reland of [Android][Telemetry] Add support for multiple power monitors

tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor_unittest.py

Index: tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor_unittest.py
diff --git a/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor_unittest.py b/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor_unittest.py
index f79d75b5da1ef57f1154b8a872da1fdadd9d3347..4ed6ea0052eb8e25d4ab42d5d6125c4ac56e88b1 100644
--- a/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor_unittest.py
+++ b/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor_unittest.py
@@ -245,3 +245,34 @@
     result = android_platform_backend.AndroidPlatformBackend.ParseCStateSample(
         cstate)
     self.assertDictEqual(expected_result, result)
+
+  def testStandAlone(self):
+    class PlatformStub(object):
+      def __init__(self, run_command_return_value):
+        self._run_command_return_value = run_command_return_value
+      def RunCommand(self, _cmd):
+        return self._run_command_return_value
+
+    cpu_state_from_samsung_note3 = (
+        "C0\n\nC1\n\nC2\n\nC3\n\n"
+        "53658520886\n1809072\n7073\n1722554\n"
+        "1\n35\n300\n500\n"
+        "1412949256\n")
+    expected_cstate_dict = {
+        'C0': 1412895593940415,
+        'C1': 1809072,
+        'C2': 7073,
+        'C3': 1722554,
+        'WFI': 53658520886
+    }
+    cpus = ["cpu%d" % cpu for cpu in range(2)]
+    expected_result = dict(zip(cpus, [expected_cstate_dict]*len(cpus)))
+
+    sysfsmon = sysfs_power_monitor.SysfsPowerMonitor(
+        PlatformStub(cpu_state_from_samsung_note3), standalone=True)
+    # pylint: disable=W0212
+    sysfsmon._cpus = cpus
+    cstate = sysfsmon.GetCpuState()
+    result = android_platform_backend.AndroidPlatformBackend.ParseCStateSample(
+        cstate)
+    self.assertDictEqual(expected_result, result)