Gracefully handle failed Mojo calls in the NotificationManager

third_party/WebKit/Source/modules/notifications/NotificationManager.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/notifications/NotificationManager.h"
 
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "modules/notifications/Notification.h"
 #include "modules/notifications/NotificationPermissionCallback.h"
@@ skipping 35 matching lines @@
 NotificationManager::~NotificationManager() {}
 
 mojom::blink::PermissionStatus NotificationManager::GetPermissionStatus(
     ExecutionContext* execution_context) {
   if (!notification_service_) {
     Platform::Current()->GetInterfaceProvider()->GetInterface(
         mojo::MakeRequest(&notification_service_));
   }
 
   mojom::blink::PermissionStatus permission_status;
-  const bool result = notification_service_->GetPermissionStatus(
-      execution_context->GetSecurityOrigin()->ToString(), &permission_status);
-  DCHECK(result);
+  if (!notification_service_->GetPermissionStatus(
+          execution_context->GetSecurityOrigin()->ToString(),
+          &permission_status)) {
+    NOTREACHED();
+    return mojom::blink::PermissionStatus::DENIED;
+  }
 
   return permission_status;
 }
 
 ScriptPromise NotificationManager::RequestPermission(
     ScriptState* script_state,
     NotificationPermissionCallback* deprecated_callback) {
   ExecutionContext* context = ExecutionContext::From(script_state);
 
   if (!permission_service_) {
@@ skipping 32 matching lines @@
 
 void NotificationManager::OnPermissionServiceConnectionError() {
   permission_service_.reset();
 }
 
 DEFINE_TRACE(NotificationManager) {
   Supplement<ExecutionContext>::Trace(visitor);
 }
 
 }  // namespace blink