[telemetry] Drop data for sysfs power monitor if distribution changes but total does not.

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

Index: tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor_unittest.py
diff --git a/tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor_unittest.py b/tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor_unittest.py
index 1a57f5b65af440f5350e1329f7daee74cb906609..6ba2cc892c1b3ea6ce89574e49d9a2882c68767d 100644
--- a/tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor_unittest.py
+++ b/tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor_unittest.py
@@ -195,6 +195,26 @@ class SysfsPowerMonitorMonitorTest(unittest.TestCase):
         self.assertAlmostEqual(results[cpu][freq],
                                self.expected_freq_percents[cpu][freq])
 
+  def testComputeCpuStatsWithMissingData(self):
+    results = sysfs_power_monitor.SysfsPowerMonitor.ComputeCpuStats(
+        {'cpu1': {}}, {'cpu1': {}})
+    self.assertEqual(results['cpu1'][12345], 0)
+
+    results = sysfs_power_monitor.SysfsPowerMonitor.ComputeCpuStats(
+        {'cpu1': {123: 0}}, {'cpu1': {123: 0}})
+    self.assertEqual(results['cpu1'][123], 0)
+
+    results = sysfs_power_monitor.SysfsPowerMonitor.ComputeCpuStats(
+        {'cpu1': {123: 456}}, {'cpu1': {123: 456}})
+    self.assertEqual(results['cpu1'][123], 0)
+
+  def testComputeCpuStatsWithNumberChange(self):
+    results = sysfs_power_monitor.SysfsPowerMonitor.ComputeCpuStats(
+        {'cpu1': {'C0': 10, 'WFI': 20}},
+        {'cpu1': {'C0': 20, 'WFI': 10}})
+    self.assertEqual(results['cpu1']['C0'], 0)
+    self.assertEqual(results['cpu1']['WFI'], 0)
+
   def testGetCpuStateForAndroidDevices(self):
     class PlatformStub(object):
       def __init__(self, run_command_return_value):