Move InstanceID field trial check to extension-specific code

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

Index: chrome/browser/extensions/api/instance_id/instance_id_api.cc
diff --git a/chrome/browser/extensions/api/instance_id/instance_id_api.cc b/chrome/browser/extensions/api/instance_id/instance_id_api.cc
index f7cdbe2c27031057d18d5e7b8f8f40b2b936696b..1c18eb5073cd71657af26234c497ef6b9fa360b5 100644
--- a/chrome/browser/extensions/api/instance_id/instance_id_api.cc
+++ b/chrome/browser/extensions/api/instance_id/instance_id_api.cc
@@ -5,6 +5,7 @@
 #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"
@@ -17,6 +18,9 @@ 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.";
@@ -74,7 +78,12 @@ ExtensionFunction::ResponseAction InstanceIDApiFunction::Run() {
 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 {