Add support for GCM subtypes to desktop Instance ID implementation

ios/chrome/browser/services/gcm/ios_chrome_gcm_profile_service_factory.cc

Index: ios/chrome/browser/services/gcm/ios_chrome_gcm_profile_service_factory.cc
diff --git a/ios/chrome/browser/services/gcm/ios_chrome_gcm_profile_service_factory.cc b/ios/chrome/browser/services/gcm/ios_chrome_gcm_profile_service_factory.cc
index abe148c203262355df0d8991b94d1f0454b14f48..35db7f15f76565e9b6cd4b45e050a9782448bdfc 100644
--- a/ios/chrome/browser/services/gcm/ios_chrome_gcm_profile_service_factory.cc
+++ b/ios/chrome/browser/services/gcm/ios_chrome_gcm_profile_service_factory.cc
@@ -32,6 +32,18 @@ IOSChromeGCMProfileServiceFactory::GetInstance() {
   return base::Singleton<IOSChromeGCMProfileServiceFactory>::get();
 }
 
+// static
+std::string IOSChromeGCMProfileServiceFactory::GetProductCategoryForSubtypes() {
+#if defined(GOOGLE_CHROME_BUILD)
+  std::string channel = ::GetChannelString();
+  if (channel.empty())
+    channel = "stable";
+  return "com.chrome." + channel + ".ios";
+#else
+  return "org.chromium.unknown.ios";
+#endif
+}
+
 IOSChromeGCMProfileServiceFactory::IOSChromeGCMProfileServiceFactory()
     : BrowserStateKeyedServiceFactory(
           "GCMProfileService",
@@ -57,6 +69,7 @@ IOSChromeGCMProfileServiceFactory::BuildServiceInstanceFor(
   return base::WrapUnique(new gcm::GCMProfileService(
       browser_state->GetPrefs(), browser_state->GetStatePath(),
       browser_state->GetRequestContext(), ::GetChannel(),
+      GetProductCategoryForSubtypes(),
       base::WrapUnique(new ProfileIdentityProvider(
           ios::SigninManagerFactory::GetForBrowserState(browser_state),
           OAuth2TokenServiceFactory::GetForBrowserState(browser_state),