Stop the existing session if it exists before start a new session and add mirroring scenario for cp…

chrome/test/media_router/media_router_perf_tests.isolate

 # Copyright (c) 2016 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.
 {
   'conditions': [
     ['OS=="linux" or OS=="mac" or OS=="win"', {
       'variables': {
         'command': [
           'python',
           'telemetry/run_benchmark',
           '--browser=release',
           '--also-run-disabled-tests',
           '-v',
-          '--output-format=chartjson',
           '--output-dir=${ISOLATED_OUTDIR}',
         ],
         'files': [
           'internal/',
           '<(PRODUCT_DIR)/mr_extension/release/',
           '<(PRODUCT_DIR)/media_router/test_extension/',
           '../../../third_party/catapult/',
           '../../../tools/perf/',
           '../../../tools/variations/fieldtrial_util.py',
           'telemetry/',
         ],
       },
     }],
   ],
   'includes': [
     '../../chrome.isolate',
   ],
 }