Update cpu and memory metric calculation and several small improvements.

chrome/test/media_router/telemetry/media_router_config.py

 # Copyright 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.
 
 import os
 import sys
 
 # Add //tools/perf/ to system path.
 sys.path.append(os.path.join(os.path.dirname(__file__),
                              os.pardir, os.pardir, os.pardir,
                              os.pardir, 'tools', 'perf'))
 
+# Add //chrome/test/media_router/internal to system path.
+sys.path.append(os.path.join(os.path.dirname(__file__),
+                                 os.pardir, 'internal'))
+
 from chrome_telemetry_build import chromium_config
 
 TELEMETRY_DIR = chromium_config.GetTelemetryDir()
 
 _top_level_dir = os.path.dirname(os.path.realpath(__file__))
 
 
 def Config(benchmark_subdirs):
   return chromium_config.ChromiumConfig(
       top_level_dir=_top_level_dir,
       benchmark_dirs=[os.path.join(_top_level_dir, subdir)
                       for subdir in benchmark_subdirs])