[Telemetry] Always clean up startup config file on Android

telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py

Index: telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
diff --git a/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py b/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
index 2f311bff214d4d18dec1c8064fee53eb3b15173c..d6485212e31c5c872c96612047e94111e007a667 100644
--- a/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
+++ b/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import atexit
 import logging
 import os
 import shutil
@@ -154,6 +155,9 @@ class ChromeTracingAgent(tracing_agent.TracingAgent):
                                              _CHROME_TRACE_CONFIG_FILE_NAME)
       self._platform_backend.device.WriteFile(self._trace_config_file,
           self._CreateTraceConfigFileString(config), as_root=True)
+      # The config file has fixed path on Android. We need to ensure it is
+      # always cleaned up.
+      atexit.register(self._RemoveTraceConfigFile)

[nednguyen, 2016/03/25 00:23:59]

Where is the place that fail to call StopAgentTracing exactly? I just learn that
the atexit is not bullet proof since if process is killed by SIGTERM, this will
not be called.

     elif self._platform_backend.GetOSName() in _DESKTOP_OS_NAMES:
       self._trace_config_file = os.path.join(tempfile.mkdtemp(),
                                              _CHROME_TRACE_CONFIG_FILE_NAME)