Adding a test for measuring memory usage.

tools/perf/perf_tools/memory_benchmark.py

+# Copyright (c) 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 telemetry import multi_page_benchmark
+
+MEMORY_HISTOGRAMS = [
+    {'name': 'V8.MemoryExternalFragmentationTotal', 'units': 'percent'},
+    {'name': 'V8.MemoryHeapSampleTotalCommitted', 'units': 'kb'},
+    {'name': 'V8.MemoryHeapSampleTotalUsed', 'units': 'kb'}]
+
+class MemoryBenchmark(multi_page_benchmark.MultiPageBenchmark):
+  def __init__(self):
+    super(MemoryBenchmark, self).__init__()
+
+  def CustomizeBrowserOptions(self, options):
+    options.AppendExtraBrowserArg('--dom-automation')
+
+  def CanRunForPage(self, page):
+    return hasattr(page, 'stress_memory')
+
+  def MeasurePage(self, page, tab, results):
+    for histogram in MEMORY_HISTOGRAMS:
+      name = histogram['name']
+      data = tab.runtime.Evaluate(
+          'window.domAutomationController.getHistogram("%s")' % name)
+      results.Add(name, histogram['units'], data, data_type='histogram')
+
+  def GetInteractionName(self):

[nduca, 2012/11/12 20:58:12]

why not an init-time constructor?

if it was init time, then you coudl throw an exception at that point if the
interaction class didn't exist

[marja, 2012/11/12 21:35:26]

Hmm? Init-time constructor of which class? Do you want to keep the information
that the interaction to run is "stress_memory" in this file, or do you want me
to move it to somewhere else?

[marja, 2012/11/13 09:47:40]

Ok, made it a ctor parameter for PageTest. But we can't thrown an exception at
that time:

We're passing 'stress_memory' to PageTest, and in the json for a page, we either
have

'stress_memory': {'action': 'foo'}

or not, and it's completely ok to not have stress_memory for any page; also in
the ctor of PageTest we don't know the specific pages yet, so we can't throw an
exception if 'foo' is not an action.

+    return 'stress_memory'