[Android][telemetry] Break logging deadlock when attempting to log an AppCrashException.

tools/telemetry/telemetry/core/exceptions.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 sys
 
 
 class Error(Exception):
   """Base class for Telemetry exceptions."""
   def __init__(self, msg=''):
@@ skipping 35 matching lines @@
 
   It is possible that waiting for a longer period of time would result in a
   successful operation.
   """
   pass
 
 
 class AppCrashException(Error):
   def __init__(self, app=None, msg=''):
     super(AppCrashException, self).__init__(msg)
-    self._app = app
     self._msg = msg
+    self._stack_trace = app.GetStackTrace() if app else None
 
   def __str__(self):
-    if not self._app:
+    if not self._stack_trace:
       return super(AppCrashException, self).__str__()
     divider = '*' * 80
     return '%s\nStack Trace:\n%s\n\t%s\n%s' % (
         super(AppCrashException, self).__str__(), divider,
-        self._app.GetStackTrace().replace('\n', '\n\t'), divider)
+        self._stack_trace.replace('\n', '\n\t'), divider)
 
 
 class DevtoolsTargetCrashException(AppCrashException):
   """Represents a crash of the current devtools target but not the overall app.
 
   This can be a tab or a WebView. In this state, the tab/WebView is
   gone, but the underlying browser is still alive.
   """
   def __init__(self, app, msg='Devtools target crashed'):
     super(DevtoolsTargetCrashException, self).__init__(app, msg)
@@ skipping 46 matching lines @@
   """ Represents an exception when encountering an unsupported Android APK. """
 
 
 class PackageDetectionError(Error):
   """ Represents an error when parsing an Android APK's package. """
 
 
 class AndroidDeviceParsingError(Error):
   """Represents an error when parsing output from an android device"""