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 59da7345668fa53fde00def1e321d42770ab08e4..b6a41b4f14aa63dfba28c64f82e1148f1aadd4fa 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]
 
 
@@ -64,3 +66,36 @@ 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 = {
+        2901000000: 28560119,
+        2900000000: 20,
+        2800000000: 2,
+        2700000000: 32,
+        2500000000: 3,
+        2400000000: 4,
+        2300000000: 0,
+        2200000000: 0,
+        2000000000: 0,
+        1900000000: 0,
+        1800000000: 0,
+        1700000000: 0,
+        1600000000: 0,
+        1400000000: 0,
+        1300000000: 0,
+        1200000000: 0,
+    }
+    self.assertEquals(expected, result['GlobalCpuFrequencyStats'])