Remove DeferBackgroundExtensionCreation field trial and supporting code

chrome/browser/sync/test/integration/sync_extension_helper.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/sync/test/integration/sync_extension_helper.h"
 
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/values.h"
@@ skipping 235 matching lines @@
                << " do not match profile " << profile2->GetDebugName();
       return false;
     }
     ++it1;
     ++it2;
   }
   return true;
 }
 
 void SyncExtensionHelper::SetupProfile(Profile* profile) {
-  extensions::ExtensionSystem::Get(profile)->InitForRegularProfile(true, false);
+  extensions::ExtensionSystem::Get(profile)->InitForRegularProfile(true);
   profile_extensions_.insert(make_pair(profile, ExtensionNameMap()));
 }
 
 namespace {
 
 std::string NameToPublicKey(const std::string& name) {
   std::string public_key;
   std::string pem;
   EXPECT_TRUE(Extension::ProducePEM(name, &pem) &&
               Extension::FormatPEMForFileOutput(pem, &public_key,
@@ skipping 103 matching lines @@
     EXPECT_EQ(expected_id, extension->id());
     return NULL;
   }
   DVLOG(2) << "created extension with name = "
            << name << ", id = " << expected_id;
   (it->second)[name] = extension;
   id_to_name_[expected_id] = name;
   id_to_type_[expected_id] = type;
   return extension;
 }