Add experiment groups for <link rel=prefetch> experiment.

chrome/common/metrics/variations/variation_ids.h

 // 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.
 
 #ifndef CHROME_COMMON_METRICS_VARIATIONS_VARIATION_IDS_H_
 #define CHROME_COMMON_METRICS_VARIATIONS_VARIATION_IDS_H_
 
 namespace chrome_variations {
 
 // A list of Chrome Variation IDs. These IDs are associated with FieldTrials
@@ skipping 286 matching lines @@
   IOS_TABLET_NEW_NTP_CONTROL_2_BETA = 3312107,
   IOS_TABLET_NEW_NTP_OMNIBOX_HINT_STABLE = 3312108,
   IOS_TABLET_NEW_NTP_CONTROL_1_STABLE = 3312109,
   IOS_TABLET_NEW_NTP_FAKEBOX_HINT_STABLE = 3312110,
   IOS_TABLET_NEW_NTP_CONTROL_2_STABLE = 3312111,
 
   // ExtensionInstallPrompt field trial.
   EXTENSION_INSTALL_PROMPT_EXPERIMENT_ID_MIN = 3312051,
   EXTENSION_INSTALL_PROMPT_EXPERIMENT_ID_MAX = 3312099,
 
+  // <link rel=prefetch> field trial.
+  LINK_REL_PREFETCH_ENABLED_1 = 3312118,
+  LINK_REL_PREFETCH_ENABLED_2 = 3312119,
+  LINK_REL_PREFETCH_DISABLED_1 = 3312120,
+  LINK_REL_PREFETCH_DISABLED_2 = 3312121,
+
   // NEXT ID: When adding new IDs, please add them above this section, starting
   // with the value of NEXT_ID, and updating NEXT_ID to (end of your reserved
   // range) + 1.
-  NEXT_ID = 3312118,
+  NEXT_ID = 3312122,
 
   // USABLE IDs END HERE.
   //
   // The largest possible Chrome variation ID in the reserved range. When
   // defining your variation IDs, DO NOT exceed this value - GWS will ignore
   // your experiment!
   MAXIMUM_ID = 3399999,
 };
 
 }  // namespace chrome_variations
 
 #endif  // CHROME_COMMON_METRICS_VARIATIONS_VARIATION_IDS_H_