Telemetry: adds CPU frequency stats.

tools/telemetry/telemetry/core/platform/proc_supporting_platform_backend_unittest.py

Index: tools/telemetry/telemetry/core/platform/proc_supporting_platform_backend_unittest.py
diff --git a/tools/telemetry/telemetry/core/platform/proc_supporting_platform_backend_unittest.py b/tools/telemetry/telemetry/core/platform/proc_supporting_platform_backend_unittest.py
index 81069b841cf3dec57ea2888aa99cd33d5f8d33f1..0e5a6a2766b8f88e33b38fb2ac15239a8a3b2d0d 100644
--- a/tools/telemetry/telemetry/core/platform/proc_supporting_platform_backend_unittest.py
+++ b/tools/telemetry/telemetry/core/platform/proc_supporting_platform_backend_unittest.py
@@ -22,6 +22,8 @@ class TestBackend(
     self._mock_files[filename] = output
 
   def _GetFileContents(self, filename):
+    if filename not in self._mock_files:
+      raise IOError(filename)
     return self._mock_files[filename]
 
 
@@ -70,3 +72,36 @@ class ProcSupportingPlatformBackendTest(unittest.TestCase):
                                'VMPeak': 1025978368,
                                'WorkingSetSize': 84000768,
                                'WorkingSetSizePeak': 84000768})
+
+  def testGlobalCpuStats(self):
+    if not proc_supporting_platform_backend.resource:
+      logging.warning('Test not supported')
+      return
+
+    backend = TestBackend()
+    backend.SetMockFile('/sys/devices/system/cpu/kernel_max', '63')
+    for cpu in range(2, 5):
+      backend.SetMockFile(
+          '/sys/devices/system/cpu/cpu%d/cpufreq/stats/time_in_state' % cpu,
+          open(os.path.join(util.GetUnittestDataDir(),
+              'cpu_%d_time_in_state' % cpu)).read())
+    result = backend.GetGlobalCpuStats()
+    expected = {
+        2901000: 28560119,
+        2900000: 20,
+        2800000: 2,
+        2700000: 32,
+        2500000: 3,
+        2400000: 4,
+        2300000: 0,
+        2200000: 0,
+        2000000: 0,
+        1900000: 0,
+        1800000: 0,
+        1700000: 0,
+        1600000: 0,
+        1400000: 0,
+        1300000: 0,
+        1200000: 0,
+    }
+    self.assertEquals(expected, result['GlobalCpuFrequencyStats'])