[Android] Switch to DeviceUtils versions of file functions.

build/android/pylib/perf/perf_control_unittest.py

Index: build/android/pylib/perf/perf_control_unittest.py
diff --git a/build/android/pylib/perf/perf_control_unittest.py b/build/android/pylib/perf/perf_control_unittest.py
index 9333dbce85f9bebe2ff3dd9a9b20384c578518b7..aa31f68d010531ab2ff84fbfd1bd25e90f25b565 100644
--- a/build/android/pylib/perf/perf_control_unittest.py
+++ b/build/android/pylib/perf/perf_control_unittest.py
@@ -30,10 +30,10 @@ class TestPerfControl(unittest.TestCase):
       for cpu in range(perf._num_cpu_cores):
         path = perf_control.PerfControl._CPU_ONLINE_FMT % cpu
         self.assertEquals('1',
-                          self._device.old_interface.GetFileContents(path)[0])
+                          self._device.ReadFile(path)[0])
         path = perf_control.PerfControl._SCALING_GOVERNOR_FMT % cpu
         self.assertEquals('performance',
-                          self._device.old_interface.GetFileContents(path)[0])
+                          self._device.ReadFile(path)[0])
     finally:
       perf.SetDefaultPerfMode()