Remove an exception when using telemetry without cloud storage rights.

When running telemetry on my personal laptop (without any specific rights), using a open-source flow, I get the error below. 

The code assumes the access to cloud storage to read the credentials file. Page cycler seems to work without credentials and skip page that could not be accessed.

This CL removes the dependency to the could by ignoring the credentials file.

% python run_measurement page_cycler page_sets\top_10.js

Traceback (most recent call last):
  <module> at tools\perf\run_measurement:128
    sys.exit(Main())
  Main at tools\perf\run_measurement:124
    return runner.Run(new_perf_path, page_set_filenames)
  Run at tools\telemetry\telemetry\page\page_test_runner.py:39
    page_set_filenames)
  ParseCommandLine at tools\telemetry\telemetry\page\page_test_runner.py:163
    ps = self.GetPageSet(test, page_set_filenames)
  GetPageSet at tools\telemetry\telemetry\page\page_test_runner.py:102
    return page_set.PageSet.FromFile(page_set_arg)
  FromFile at tools\telemetry\telemetry\page\page_set.py:86
    return cls.FromDict(data, file_path)
  FromDict at tools\telemetry\telemetry\page\page_set.py:90
    return cls(file_path, data)
  __init__ at tools\telemetry\telemetry\page\page_set.py:60
    os.path.join(self._base_dir, self.credentials_path))
  GetIfChanged at tools\telemetry\telemetry\page\cloud_storage.py:183
    _RunCommand(['cp', url, file_path])
  _RunCommand at tools\telemetry\telemetry\page\cloud_storage.py:110
    raise CredentialsError(gsutil_path)


The error is replaced by:

% python run_measurement page_cycler page_sets\top_10.json
WARNING:root:Cannot retrieve credential file: data/credentials.json


R=tonyg@chromium.org, nduca@chromium.org

BUG=333609

Review URL: https://codereview.chromium.org/148363002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249869 0039d316-1c4b-4281-b951-d872f2087c98
Don't call RenderProcessHostImpl::WebRtcLogMessage() if ENABLE_WEBRTC=0.

BUG=341122

Review URL: https://codereview.chromium.org/140093006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249870 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249870