Reland of Migrate DeviceUtils.ReadFile to adb_wrapper

build/android/pylib/instrumentation/test_runner.py

 # Copyright (c) 2012 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.
 
 """Class for running instrumentation tests on a single device."""
 
 import logging
 import os
 import re
 import sys
@@ skipping 217 matching lines @@
     # us so we know to ignore the results.
     # The --NORUN-- tag is managed by MainActivityTestBase.java
     if regex.group(1) != '--NORUN--':
 
       # Obtain the relevant perf data.  The data is dumped to a
       # JSON formatted file.
       json_string = self.device.ReadFile(
           '/data/data/com.google.android.apps.chrome/files/PerfTestData.txt',
           as_root=True)
 
-      if json_string:
-        json_string = '\n'.join(json_string)
-      else:
-        raise Exception('Perf file does not exist or is empty')
+      if not json_string:
+        raise Exception('Perf file is empty')
 
       if self.options.save_perf_json:
         json_local_file = '/tmp/chromium-android-perf-json-' + raw_test_name
         with open(json_local_file, 'w') as f:
           f.write(json_string)
         logging.info('Saving Perf UI JSON from test ' +
                      test + ' to ' + json_local_file)
 
       raw_perf_data = regex.group(1).split(';')
 
@@ skipping 212 matching lines @@
     except device_errors.CommandTimeoutError as e:
       results.AddResult(test_result.InstrumentationTestResult(
           test, base_test_result.ResultType.TIMEOUT, start_ms, duration_ms,
           log=str(e) or 'No information'))
     except device_errors.DeviceUnreachableError as e:
       results.AddResult(test_result.InstrumentationTestResult(
           test, base_test_result.ResultType.CRASH, start_ms, duration_ms,
           log=str(e) or 'No information'))
     self.TestTeardown(test, results)
     return (results, None if results.DidRunPass() else test)