Push API: Validate storage before returning cached subscriptions

components/gcm_driver/gcm_driver_android.cc

Index: components/gcm_driver/gcm_driver_android.cc
diff --git a/components/gcm_driver/gcm_driver_android.cc b/components/gcm_driver/gcm_driver_android.cc
index a512e8248d9a045c091c9c2440ec80577d1b26d8..a0fedd5cf650ea7b0d940baba5007154aff8f961 100644
--- a/components/gcm_driver/gcm_driver_android.cc
+++ b/components/gcm_driver/gcm_driver_android.cc
@@ -13,6 +13,7 @@
 #include "base/android/jni_string.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "jni/GCMDriver_jni.h"
 
 using base::android::AppendJavaStringArrayToStringVector;
@@ -117,6 +118,16 @@ bool GCMDriverAndroid::RegisterJni(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
+void GCMDriverAndroid::ValidateRegistration(
+    const std::string& app_id,
+    const std::vector<std::string>& sender_ids,
+    const std::string& registration_id,
+    const ValidateRegistrationCallback& callback) {
+  // gcm_driver doesn't store registration IDs on Android, so assume it's valid.

[Peter Beverloo, 2017/03/20 23:50:13]

Is there something we could do here long-term, like check with GMScore?

[johnme, 2017/03/30 18:36:38]

No, GMSCore has a cache, but it expires, and there's no way to query it without
registering. More importantly, even if our stored registration is out of sync
with GMSCore's cache, GMSCore will happily forward messages that are sent to our
stored registration - i.e. unlike GCMClientImpl, GMSCore doesn't require that
incoming messages match its stored registrations.

+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(callback, true /* is_valid */));
+}
+
 void GCMDriverAndroid::OnSignedIn() {
 }