Enable InstanceID field trial by default

components/gcm_driver/instance_id/instance_id_driver.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 "components/gcm_driver/instance_id/instance_id_driver.h"
 
 #include "base/metrics/field_trial.h"
 #include "build/build_config.h"
 #include "components/gcm_driver/gcm_driver.h"
 #include "components/gcm_driver/instance_id/instance_id.h"
 
 namespace instance_id {
 
 namespace {
 const char kInstanceIDFieldTrialName[] = "InstanceID";
-const char kInstanceIDFieldTrialEnabledGroupName[] = "Enabled";
+const char kInstanceIDFieldTrialDisabledGroupName[] = "Disabled";
 }  // namespace
 
 // static
 bool InstanceIDDriver::IsInstanceIDEnabled() {
   std::string group_name =
       base::FieldTrialList::FindFullName(kInstanceIDFieldTrialName);
-  return group_name == kInstanceIDFieldTrialEnabledGroupName;
+  return group_name != kInstanceIDFieldTrialDisabledGroupName;

[Alexei Svitkine (slow), 2016/04/08 15:11:03]

Our best practices recommend using StartsWith() for group checks. This way, you
can have differently named groups with the same behavior - which is useful for
example when tweaking percentages to prevent biases from the old population.

[johnme, 2016/04/08 15:28:10]

Done (I used case-insensitive StartsWith, since it seems that'd reduce the
danger of typos).

 }
 
 InstanceIDDriver::InstanceIDDriver(gcm::GCMDriver* gcm_driver)
     : gcm_driver_(gcm_driver) {
 }
 
 InstanceIDDriver::~InstanceIDDriver() {
 }
 
 InstanceID* InstanceIDDriver::GetInstanceID(const std::string& app_id) {
@@ skipping 11 matching lines @@
 
 void InstanceIDDriver::RemoveInstanceID(const std::string& app_id) {
   instance_id_map_.erase(app_id);
 }
 
 bool InstanceIDDriver::ExistsInstanceID(const std::string& app_id) const {
   return instance_id_map_.find(app_id) != instance_id_map_.end();
 }
 
 }  // namespace instance_id