[Telemetry] Allow page cycler to run on devices that don't report CommitCharge.

tools/perf/metrics/memory.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.
 
 import sys
 
 from metrics import histogram_util
 from metrics import Metric
 from telemetry.value import histogram
 from telemetry.value import scalar
@@ skipping 41 matching lines @@
 class MemoryMetric(Metric):
   """MemoryMetric gathers memory statistics from the browser object.
 
   This includes both per-page histogram stats, most about javascript
   memory usage, and overall memory stats from the system for the whole
   test run."""
 
   def __init__(self, browser):
     super(MemoryMetric, self).__init__()
     self._browser = browser
-    self._start_commit_charge = self._browser.memory_stats['SystemCommitCharge']
+    start_memory_stats = self._browser.memory_stats
+    self._start_commit_charge = None
+    if 'SystemCommitCharge' in start_memory_stats:
+      self._start_commit_charge = start_memory_stats['SystemCommitCharge']
     self._memory_stats = None
     self._histogram_start = dict()
     self._histogram_delta = dict()
 
   @classmethod
   def CustomizeBrowserOptions(cls, options):
     options.AppendExtraBrowserArgs([
         '--enable-stats-collection-bindings',
         # For a hard-coded set of Google pages (such as GMail), we produce
         # custom memory histograms (V8.Something_gmail) instead of the generic
@@ skipping 45 matching lines @@
       results.AddValue(histogram.HistogramValue(
           results.current_page, h['display_name'], h['units'],
           raw_value_json=self._histogram_delta[h['name']], important=False,
           description=h.get('description')))
     self._memory_stats = self._browser.memory_stats
     if not self._memory_stats['Browser']:
       return
     AddResultsForProcesses(results, self._memory_stats,
                            metric_trace_name=trace_name)
 
-    end_commit_charge = self._memory_stats['SystemCommitCharge']
-    commit_charge_difference = end_commit_charge - self._start_commit_charge
-    results.AddValue(scalar.ScalarValue(
-        results.current_page,
-        'commit_charge.' + (trace_name or 'commit_charge'),
-        'kb', commit_charge_difference, important=False,
-        description='System commit charge (committed memory pages).'))
+    if self._start_commit_charge:
+      end_commit_charge = self._memory_stats['SystemCommitCharge']
+      commit_charge_difference = end_commit_charge - self._start_commit_charge
+      results.AddValue(scalar.ScalarValue(
+          results.current_page,
+          'commit_charge.' + (trace_name or 'commit_charge'),
+          'kb', commit_charge_difference, important=False,
+          description='System commit charge (committed memory pages).'))
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'processes.' + (trace_name or 'processes'),
         'count', self._memory_stats['ProcessCount'], important=False,
         description='Number of processes used by Chrome.'))
 
 
 def AddResultsForProcesses(results, memory_stats, chart_trace_name='final',
                            metric_trace_name=None,
                            exclude_metrics=None):
   """Adds memory stats for browser, renderer and gpu processes.
@@ skipping 74 matching lines @@
     AddResult('VMPeak', 'vm_peak_size',
               'The peak Virtual Memory Size (address space allocated) usage '
               'achieved by the * process.')
     AddResult('WorkingSetSizePeak', '%s_peak_size' % metric,
               'Peak Working Set Size.')
 
   AddResultsForProcessTypes(['Browser'], 'browser')
   AddResultsForProcessTypes(['Renderer'], 'renderer')
   AddResultsForProcessTypes(['Gpu'], 'gpu')
   AddResultsForProcessTypes(['Browser', 'Renderer', 'Gpu'], 'total')