Delete now unused PageMeasurement class.

tools/perf/metrics/__init__.py

 # Copyright 2013 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.
 
 class Metric(object):
   """Base class for all the metrics that are used by telemetry measurements.
 
   The Metric class represents a way of measuring something. Metrics are
-  helper classes used by PageMeasurements. Each PageMeasurement may use
+  helper classes used by PageTests. Each PageTest may use
   multiple metrics; each metric should be focussed on collecting data
   about one thing.
   """
 
   @classmethod
   def CustomizeBrowserOptions(cls, options):
     """Add browser options that are required by this metric.
 
     Some metrics do not have any special browser options that need
     to be added, and they do not need to override this method; by
     default, no browser options are added.
 
     To add options here, call options.AppendExtraBrowserArgs(arg).
     """
     pass
 
   def Start(self, page, tab):
     """Start collecting data for this metric."""
     pass
 
   def Stop(self, page, tab):
     """Stop collecting data for this metric (if applicable)."""
     pass
 
   def AddResults(self, tab, results):
     """Add the data collected into the results object for a measurement.
 
     Metrics may implement AddResults to provide a common way to add results
-    to the PageTestResults in PageMeasurement.AddMeasurement --
+    to the PageTestResults in PageTest.ValidateOrMeasurePage --
     results should be added with results.AddValue(...).
     """
     raise NotImplementedError()