CrOS: Add print statements to help debug BrowserProcessImpl::Unpin crash.

chrome/browser/push_messaging/push_messaging_service_impl.h

Index: chrome/browser/push_messaging/push_messaging_service_impl.h
diff --git a/chrome/browser/push_messaging/push_messaging_service_impl.h b/chrome/browser/push_messaging/push_messaging_service_impl.h
index 920f44e8180b6d20c1d5ff1835888729027a12ed..b5ebac1256533e254d003f4c9ca19591aa41c10b 100644
--- a/chrome/browser/push_messaging/push_messaging_service_impl.h
+++ b/chrome/browser/push_messaging/push_messaging_service_impl.h
@@ -26,6 +26,8 @@
 #include "components/gcm_driver/gcm_client.h"
 #include "components/gcm_driver/instance_id/instance_id.h"
 #include "components/keyed_service/core/keyed_service.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/push_messaging_service.h"
 #include "content/public/common/push_event_payload.h"
 #include "content/public/common/push_messaging_status.h"
@@ -47,6 +49,7 @@ class InstanceIDDriver;
 }
 
 class PushMessagingServiceImpl : public content::PushMessagingService,
+                                 public content::NotificationObserver,
                                  public gcm::GCMAppHandler,
                                  public content_settings::Observer,
                                  public KeyedService,
@@ -71,6 +74,11 @@ class PushMessagingServiceImpl : public content::PushMessagingService,
                           const std::string& message_id) override;
   bool CanHandle(const std::string& app_id) const override;
 
+  // content::NotificationObserver:
+  void Observe(int type,
+               const content::NotificationSource& source,
+               const content::NotificationDetails& details) override;
+
   // content::PushMessagingService implementation:
   GURL GetEndpoint(bool standard_protocol) const override;
   void SubscribeFromDocument(const GURL& requesting_origin,
@@ -266,6 +274,8 @@ class PushMessagingServiceImpl : public content::PushMessagingService,
   std::unique_ptr<PushMessagingServiceObserver>
       push_messaging_service_observer_;
 
+  content::NotificationRegistrar registrar_;
+
 #if BUILDFLAG(ENABLE_BACKGROUND)
   // KeepAlive registered while we have in-flight push messages, to make sure
   // we can finish processing them without being interrupted.