Feature to disable field trials in old versions of Chromium. Field trials...

net/disk_cache/backend_impl.cc

 // Copyright (c) 2010 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 "net/disk_cache/backend_impl.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/message_loop.h"
 #include "base/metrics/field_trial.h"
@@ skipping 156 matching lines @@
 // Initializes the field trial structures to allow performance measurements
 // for the current cache configuration. Returns true if we are active part of
 // the CacheThrottle field trial.
 bool SetFieldTrialInfo(int size_group) {
   static bool first = true;
   if (!first)
     return false;
 
   // Field trials involve static objects so we have to do this only once.
   first = false;
+  std::string group1 = base::StringPrintf("CacheSizeGroup_%d", size_group);
   scoped_refptr<base::FieldTrial> trial1(
-      new base::FieldTrial("CacheSize", 10));
-  std::string group1 = base::StringPrintf("CacheSizeGroup_%d", size_group);
-  trial1->AppendGroup(group1, base::FieldTrial::kAllRemainingProbability);
+      new base::FieldTrial("CacheSize", 10, group1, 2011, 6, 30));
+  trial1->group();

[jar (doing other things), 2011/01/15 20:52:47]

nit: API should not require users to explicitly call group() to finalize.

 
+  // After June 30, 2011 builds, it will always be in defaut group.
   scoped_refptr<base::FieldTrial> trial2(
-      new base::FieldTrial("CacheThrottle", 100));
+      new base::FieldTrial("CacheThrottle", 100, "CacheThrottle_Default", 2011,
+          6, 30));
   int group2a = trial2->AppendGroup("CacheThrottle_On", 10);  // 10 % in.
   trial2->AppendGroup("CacheThrottle_Off", 10);  // 10 % control.
 
   return trial2->group() == group2a;
 }
 
 // ------------------------------------------------------------------------
 
 // This class takes care of building an instance of the backend.
 class CacheCreator {
@@ skipping 1901 matching lines @@
     if (total_memory > kMaxBuffersSize || total_memory <= 0)
       total_memory = kMaxBuffersSize;
 
     done = true;
   }
 
   return static_cast<int>(total_memory);
 }
 
 }  // namespace disk_cache