Move InstanceID field trial check to extension-specific code

chrome/browser/extensions/api/instance_id/instance_id_api.cc

 // Copyright 2015 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/extensions/api/instance_id/instance_id_api.h"
 
 #include "base/logging.h"
+#include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/services/gcm/instance_id/instance_id_profile_service.h"
 #include "chrome/browser/services/gcm/instance_id/instance_id_profile_service_factory.h"
 #include "chrome/common/extensions/api/instance_id.h"
 #include "components/gcm_driver/instance_id/instance_id_driver.h"
 #include "extensions/common/extension.h"
 
 namespace extensions {
 
 namespace {
 
+const char kInstanceIDFieldTrialName[] = "InstanceID";
+const char kInstanceIDFieldTrialEnabledGroupName[] = "Enabled";
+
 // Error messages.
 const char kInvalidParameter[] = "Function was called with invalid parameters.";
 const char kDisabled[] = "Instance ID is currently disabled.";
 const char kAsyncOperationPending[] = "Asynchronous operation is pending.";
 const char kNetworkError[] = "Network error occurred.";
 const char kServerError[] = "Server error occurred.";
 const char kUnknownError[] = "Unknown error occurred.";
 
 const char* InstanceIDResultToError(instance_id::InstanceID::Result result) {
   switch (result) {
@@ skipping 37 matching lines @@
     return RespondNow(Error(
         InstanceIDResultToError(instance_id::InstanceID::DISABLED)));
   }
 
   return DoWork();
 }
 
 bool InstanceIDApiFunction::IsEnabled() const {
   Profile* profile = Profile::FromBrowserContext(browser_context());
 
-  return instance_id::InstanceIDProfileService::IsInstanceIDEnabled(profile);
+  if (!instance_id::InstanceIDProfileService::IsInstanceIDEnabled(profile))
+    return false;
+
+  std::string group_name =
+      base::FieldTrialList::FindFullName(kInstanceIDFieldTrialName);
+  return group_name == kInstanceIDFieldTrialEnabledGroupName;
 }
 
 instance_id::InstanceID* InstanceIDApiFunction::GetInstanceID() const {
   return instance_id::InstanceIDProfileServiceFactory::GetForProfile(
       Profile::FromBrowserContext(browser_context()))->driver()->
           GetInstanceID(extension()->id());
 }
 
 InstanceIDGetIDFunction::InstanceIDGetIDFunction() {}
 
@@ skipping 94 matching lines @@
 
 void InstanceIDDeleteIDFunction::DeleteIDCompleted(
     instance_id::InstanceID::Result result) {
   if (result == instance_id::InstanceID::SUCCESS)
     Respond(NoArguments());
   else
     Respond(Error(InstanceIDResultToError(result)));
 }
 
 }  // namespace extensions