Add simple cache backend experiment hidden behind a flag.

chrome/browser/chrome_browser_field_trials.cc

 // 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.
 
 #include "chrome/browser/chrome_browser_field_trials.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
@@ skipping 41 matching lines @@
     const CommandLine& parsed_command_line) :
         parsed_command_line_(parsed_command_line) {
 }
 
 ChromeBrowserFieldTrials::~ChromeBrowserFieldTrials() {
 }
 
 void ChromeBrowserFieldTrials::SetupFieldTrials(
     const base::Time& install_time) {
   chrome_variations::SetupUniformityFieldTrials(install_time);
+  SetUpSimpleCacheFieldTrial();

[SteveT, 2013/03/15 14:07:05]

We might want to wrap this in a SetupAndroidFieldTrials method which can be set
to only compile on Android.

[pasko-google - do not use, 2013/03/15 15:36:28]

That makes sense in general. Right now we want it be available on all platforms
for ease of development. Hidden behind a flag.

Later we will switch the experiment to live on Android and probably iOS too. And
I did not find yet where the code for controlling iOS experiments should be
living.

 #if !defined(OS_ANDROID)
   SetupDesktopFieldTrials();
 #endif  // defined(OS_ANDROID)
 }
 
 void ChromeBrowserFieldTrials::SetupDesktopFieldTrials() {
   prerender::ConfigurePrefetchAndPrerender(parsed_command_line_);
   SpdyFieldTrial();
   WarmConnectionFieldTrial();
   AutoLaunchChromeFieldTrial();
@@ skipping 112 matching lines @@
 #if defined(OS_CHROMEOS)
   avatar_menu_always_hidden = true;
 #endif
   base::FieldTrial* trial = base::FieldTrialList::Find("ShowProfileSwitcher");
   if (trial && (!ProfileManager::IsMultipleProfilesEnabled() ||
                 avatar_menu_always_hidden)) {
     trial->Disable();
   }
 }
 
+void ChromeBrowserFieldTrials::SetUpSimpleCacheFieldTrial() {
+  if (parsed_command_line_.HasSwitch(switches::kUseSimpleCacheBackend)) {

[SteveT, 2013/03/15 14:07:05]

You want the user to turn on the switch in order to even consider rolling the
dice for the experiment?

[pasko-google - do not use, 2013/03/15 15:36:28]

Yes. This will change when we tune the experiment parameters. I outlined this in
the header file.

+    const base::FieldTrial::Probability kDivisor = 100;
+    base::FieldTrial::Probability simple_cache_probability = 100;
+    scoped_refptr<base::FieldTrial> trial(
+        base::FieldTrialList::FactoryGetFieldTrial("SimpleCacheTrial", kDivisor,
+                                                   "No", 2013, 12, 31, NULL));
+    trial->UseOneTimeRandomization();
+    trial->AppendGroup("Yes", simple_cache_probability);

[SteveT, 2013/03/15 14:07:05]

This sets up the trial so that everyone gets the "Yes" group. Is this what you
meant to do? If so, why?

Your CL description seems to imply that this is temporary and later you'll be
making changes to get the true flag behaviour.

[pasko-google - do not use, 2013/03/15 15:36:28]

Yes, exactly. It is the way to enable a 100% experiment with the flag. For
development period only.

+  }
+}
+
 void ChromeBrowserFieldTrials::SetUpCacheSensitivityAnalysisFieldTrial() {
   const base::FieldTrial::Probability kDivisor = 100;
 
   base::FieldTrial::Probability sensitivity_analysis_probability = 0;
 
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial("CacheSensitivityAnalysis",
                                                  kDivisor, "No",
                                                  2012, 12, 31, NULL));
   trial->AppendGroup("ControlA", sensitivity_analysis_probability);
@@ skipping 33 matching lines @@
   // Call |FindValue()| on the trials below, which may come from the server, to
   // ensure they get marked as "used" for the purposes of data reporting.
   base::FieldTrialList::FindValue("UMA-Dynamic-Binary-Uniformity-Trial");
   base::FieldTrialList::FindValue("UMA-Dynamic-Uniformity-Trial");
   base::FieldTrialList::FindValue("InstantDummy");
   base::FieldTrialList::FindValue("InstantChannel");
   base::FieldTrialList::FindValue("Test0PercentDefault");
   // Activate the autocomplete dynamic field trials.
   OmniboxFieldTrial::ActivateDynamicTrials();
 }