Another missed legacy_page_test module update

tools/chrome_proxy/common/chrome_proxy_metrics.py

 # Copyright 2014 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 logging
 import time
 
 from common import network_metrics
 from telemetry.page import legacy_page_test
 from telemetry.value import scalar
 
 
 CHROME_PROXY_VIA_HEADER = 'Chrome-Compression-Proxy'
 
 
-class ChromeProxyMetricException(page_test.MeasurementFailure):
+class ChromeProxyMetricException(legacy_page_test.MeasurementFailure):
   pass
 
 
 class ChromeProxyResponse(network_metrics.HTTPResponse):
   """ Represents an HTTP response from a timeline event."""
   def __init__(self, event):
     super(ChromeProxyResponse, self).__init__(event)
 
   def ShouldHaveChromeProxyViaHeader(self):
     resp = self.response
@@ skipping 81 matching lines @@
     return self.HasRequestHeader('Chrome-Proxy-Accept-Transform', "lite-page")
 
   def HasChromeProxyLitePageExpRequest(self):
     return self.HasRequestHeader('Chrome-Proxy', "exp=ignore_preview_blacklist")
 
   def HasChromeProxyLitePageResponse(self):
     return self.HasResponseHeader('Chrome-Proxy-Content-Transform', "lite-page")
 
   def HasChromeProxyPassThroughRequest(self):
     return self.HasRequestHeader('Chrome-Proxy-Accept-Transform', "identity")
-