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 937d77b4bb416cadd1d672bb16d9feffc21bfb78..7a9de7abb1487869b992885df0766fcc125e9933 100644
--- a/components/gcm_driver/instance_id/instance_id_driver.cc
+++ b/components/gcm_driver/instance_id/instance_id_driver.cc
@@ -13,14 +13,14 @@ 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)