Telemetry / Android: do not crash on GetCpuStats() if the process is gone.

Some bots are failing with:
...[0].split()
IndexError: list index out of range
This can specially happen on page cyclers,
since multiple renders can be started and killed by the
framework.

BUG=

Review URL: https://codereview.chromium.org/25002005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226642 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/telemetry/core/platform/android_platform_backend.py

@@ -86,8 +86,11 @@ class AndroidPlatformBackend(platform_backend.PlatformBackend):
       logging.warning('CPU stats cannot be retrieved on non-rooted device.')
       return {}
     stats = self._adb.GetProtectedFileContents('/proc/%s/stat' % pid,
-                                               log_result=False)[0].split()
-    return proc_util.GetCpuStats(stats)
+                                               log_result=False)
+    if not stats:
+      logging.warning('Unable to get /proc/%s/stat, process gone?', pid)
+      return {}
+    return proc_util.GetCpuStats(stats[0].split())
 
   def GetCpuTimestamp(self):
     if not self._adb.CanAccessProtectedFileContents():

tools/telemetry/telemetry/core/platform/android_platform_backend_unittest.py

+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+import unittest
+
+from telemetry.core.platform import android_platform_backend
+from telemetry.unittest import system_stub
+
+
+class MockAdbCommands(object):
+  def __init__(self, mock_content):
+    self.mock_content = mock_content
+
+  def CanAccessProtectedFileContents(self):
+    return True
+
+  # pylint: disable=W0613
+  def GetProtectedFileContents(self, file_name, log_result):
+    return self.mock_content
+
+
+class AndroidPlatformBackendTest(unittest.TestCase):
+  def setUp(self):
+    self._stubs = system_stub.Override(android_platform_backend,
+                                       ['perf_control', 'thermal_throttle'])
+
+  def tearDown(self):
+    self._stubs.Restore()
+
+  def testGetCpuStats(self):
+    proc_stat_content = [
+        '7702 (.android.chrome) S 167 167 0 0 -1 1077936448 '
+        '3247 0 0 0 4 1 0 0 20 0 9 0 5603962 337379328 5867 '
+        '4294967295 1074458624 1074463824 3197495984 3197494152 '
+        '1074767676 0 4612 0 38136 4294967295 0 0 17 0 0 0 0 0 0 '
+        '1074470376 1074470912 1102155776']
+    adb_valid_proc_content = MockAdbCommands(proc_stat_content)
+    backend = android_platform_backend.AndroidPlatformBackend(
+        adb_valid_proc_content, False)
+    cpu_stats = backend.GetCpuStats('7702')
+    self.assertEquals(cpu_stats, {'CpuProcessTime': 5.0})
+
+  def testGetCpuStatsInvalidPID(self):
+    # Mock an empty /proc/pid/stat.
+    adb_empty_proc_stat = MockAdbCommands([])
+    backend = android_platform_backend.AndroidPlatformBackend(
+        adb_empty_proc_stat, False)
+    cpu_stats = backend.GetCpuStats('7702')
+    self.assertEquals(cpu_stats, {})

tools/telemetry/telemetry/unittest/system_stub.py

@@ -14,6 +14,8 @@ import sys as real_sys
 class Override(object):
   def __init__(self, base_module, module_list):
     stubs = {'adb_commands': AdbCommandsModuleStub,
+             'perf_control': PerfControlModuleStub,
+             'thermal_throttle': ThermalThrottleModuleStub,
              'os': OsModuleStub,
              'subprocess': SubprocessModuleStub,
              'sys': SysModuleStub,
@@ -79,6 +81,24 @@ class AdbCommandsModuleStub(object):
   def HasForwarder(_=None):
     return True
 
+class PerfControlModuleStub(object):
+  class PerfControlStub(object):
+    def __init__(self, adb):
+      pass
+
+  def __init__(self):
+    self.PerfControl = PerfControlModuleStub.PerfControlStub
+
+
+class ThermalThrottleModuleStub(object):
+  class ThermalThrottleStub(object):
+    def __init__(self, adb):
+      pass
+
+  def __init__(self):
+    self.ThermalThrottle = ThermalThrottleModuleStub.ThermalThrottleStub
+
+
 class OsModuleStub(object):
   class OsPathModuleStub(object):
     def __init__(self, sys_module):