Enable InstanceID field trial by default

components/gcm_driver/instance_id/instance_id_driver.cc

Index: components/gcm_driver/instance_id/instance_id_driver.cc
diff --git a/components/gcm_driver/instance_id/instance_id_driver.cc b/components/gcm_driver/instance_id/instance_id_driver.cc
index c4c89ae5931d67d10ef20ac4db68f6f15d87ce59..1e3ee9e79edb703c0e03c6baa1b08dc2784ad3a6 100644
--- a/components/gcm_driver/instance_id/instance_id_driver.cc
+++ b/components/gcm_driver/instance_id/instance_id_driver.cc
@@ -5,6 +5,7 @@
 #include "components/gcm_driver/instance_id/instance_id_driver.h"
 
 #include "base/metrics/field_trial.h"
+#include "base/strings/string_util.h"
 #include "build/build_config.h"
 #include "components/gcm_driver/gcm_driver.h"
 #include "components/gcm_driver/instance_id/instance_id.h"
@@ -13,14 +14,15 @@ namespace instance_id {
 
 namespace {
 const char kInstanceIDFieldTrialName[] = "InstanceID";
-const char kInstanceIDFieldTrialEnabledGroupName[] = "Enabled";
+const char kInstanceIDFieldTrialDisabledGroupPrefix[] = "Disabled";
 }  // namespace
 
 // static
 bool InstanceIDDriver::IsInstanceIDEnabled() {
   std::string group_name =
       base::FieldTrialList::FindFullName(kInstanceIDFieldTrialName);
-  return group_name == kInstanceIDFieldTrialEnabledGroupName;
+  return !base::StartsWith(group_name, kInstanceIDFieldTrialDisabledGroupPrefix,
+                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
 InstanceIDDriver::InstanceIDDriver(gcm::GCMDriver* gcm_driver)