Introduce a field trial for Instant.

chrome/common/pref_names.cc

 // Copyright (c) 2011 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/common/pref_names.h"
 
 namespace prefs {
 
 // *************** PROFILE PREFS ***************
 // These are attached to the user profile
@@ skipping 251 matching lines @@
 
 // Boolean pref indicating if instant is enabled.
 const char kInstantEnabled[] = "instant.enabled";
 
 // Boolean pref indicating if instant was ever enabled.
 const char kInstantEnabledOnce[] = "instant.enabled_once";
 
 // Time when instant was last enabled.
 const char kInstantEnabledTime[] = "instant.enabled_time";
 
+// Random number drawn and used by the Instant field trial. Stored in prefs to
+// provide a consistent field trial experience across browser restarts.
+const char kInstantFieldTrialRandomDraw[] = "instant.field_trial_random_draw";

[jar (doing other things), 2011/07/22 01:42:17]

Although I understand why you're doing this... I think it is a bad idea, as it
unwittingly tags each user uniquely (I think), unless you make the resolution
rather low.  Perhaps an integer in the range of 1-100 would be sufficient for
your needs, and not provide such tagging.  WDYT?

[sreeram, 2011/07/22 14:31:16]

I think that's a fine idea! I'll change this to be a random integer in the range
[0, 10k). That will give us enough resolution to do groups of size 0.01%,
without uniquely marking the user.

+
 // Used to maintain instant promo keys. See PromoCounter for details of subkeys
 // that are used.
 const char kInstantPromo[] = "instant.promo";
 
 // Used to migrate preferences from local state to user preferences to
 // enable multiple profiles.
 // BITMASK with possible values (see browser_prefs.cc for enum):
 // 0: No preferences migrated.
 // 1: DNS preferences migrated: kDnsPrefetchingStartupList and HostReferralList
 // 2: Browser window preferences migrated: kDevToolsSplitLocation and
@@ skipping 1124 matching lines @@
 // Whether user-specified handlers for protocols and content types can be
 // specified.
 const char kCustomHandlersEnabled[] = "custom_handlers.enabled";
 
 // Integers that specify the policy refresh rate for device- and user-policy in
 // milliseconds. Not all values are meaningful, so it is clamped to a sane range
 // by the cloud policy subsystem.
 const char kDevicePolicyRefreshRate[] = "policy.device_refresh_rate";
 const char kUserPolicyRefreshRate[] = "policy.user_refresh_rate";
 }  // namespace prefs