Change PageTest.WillStartBrowser to depend on platform instead of browser object as it would not ha…

tools/perf/measurements/memory.py

 # Copyright 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.
 
 from metrics import memory
 from metrics import power
 from telemetry.page import page_test
 
 class Memory(page_test.PageTest):
   def __init__(self):
     super(Memory, self).__init__('RunStressMemory')
     self._memory_metric = None
     self._power_metric = None
 
-  def WillStartBrowser(self, browser):
-    self._power_metric = power.PowerMetric(browser)
+  def WillStartBrowser(self, platform):
+    self._power_metric = power.PowerMetric(platform)
 
   def DidStartBrowser(self, browser):
     self._memory_metric = memory.MemoryMetric(browser)
 
   def DidNavigateToPage(self, page, tab):
     self._memory_metric.Start(page, tab)
     self._power_metric.Start(page, tab)
 
   def CustomizeBrowserOptions(self, options):
     memory.MemoryMetric.CustomizeBrowserOptions(options)
     # Since this is a memory benchmark, we want to sample memory histograms at
     # a high frequency.
     options.AppendExtraBrowserArgs('--memory-metrics')
 
   def ValidateAndMeasurePage(self, page, tab, results):
     self._power_metric.Stop(page, tab)
     self._memory_metric.Stop(page, tab)
     self._memory_metric.AddResults(tab, results)
     self._power_metric.AddResults(tab, results)