Add support for the control group in the Simple Cache Experiment.

net/disk_cache/backend_impl.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 "net/disk_cache/backend_impl.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
@@ skipping 58 matching lines @@
 
 size_t GetIndexSize(int table_len) {
   size_t table_size = sizeof(disk_cache::CacheAddr) * table_len;
   return sizeof(disk_cache::IndexHeader) + table_size;
 }
 
 // ------------------------------------------------------------------------
 
 // Sets group for the current experiment. Returns false if the files should be
 // discarded.
-bool InitExperiment(disk_cache::IndexHeader* header) {
+bool InitExperiment(disk_cache::IndexHeader* header, bool cache_created) {
   if (header->experiment == disk_cache::EXPERIMENT_OLD_FILE1 ||
       header->experiment == disk_cache::EXPERIMENT_OLD_FILE2) {
     // Discard current cache.
     return false;
   }
 
+  if (base::FieldTrialList::FindFullName("SimpleCacheTrial") ==
+          "ExperimentControl") {
+    if (cache_created) {
+      header->experiment = disk_cache::EXPERIMENT_SIMPLE_CONTROL;
+      return true;
+    } else if (header->experiment != disk_cache::EXPERIMENT_SIMPLE_CONTROL) {
+      return false;
+    }
+  }
+
   header->experiment = disk_cache::NO_EXPERIMENT;
   return true;
 }
 
 // A callback to perform final cleanup on the background thread.
 void FinalCleanupCallback(disk_cache::BackendImpl* backend) {
   backend->CleanupCache();
 }
 
 }  // namespace
@@ skipping 155 matching lines @@
   }
 
   if (!CheckIndex()) {
     ReportError(ERR_INIT_FAILED);
     return net::ERR_FAILED;
   }
 
   if (!restarted_ && (create_files || !data_->header.num_entries))
     ReportError(ERR_CACHE_CREATED);
 
-  if (!(user_flags_ & kNoRandom) &&
-      cache_type_ == net::DISK_CACHE && !InitExperiment(&data_->header))
+  if (!(user_flags_ & kNoRandom) && cache_type_ == net::DISK_CACHE &&
+      !InitExperiment(&data_->header, create_files)) {
     return net::ERR_FAILED;
+  }
 
   // We don't care if the value overflows. The only thing we care about is that
   // the id cannot be zero, because that value is used as "not dirty".
   // Increasing the value once per second gives us many years before we start
   // having collisions.
   data_->header.this_id++;
   if (!data_->header.this_id)
     data_->header.this_id++;
 
   bool previous_crash = (data_->header.crash != 0);
@@ skipping 1769 matching lines @@
     if (total_memory > kMaxBuffersSize || total_memory <= 0)
       total_memory = kMaxBuffersSize;
 
     done = true;
   }
 
   return static_cast<int>(total_memory);
 }
 
 }  // namespace disk_cache