[ServiceWorker] Some code clean-up for content::ServiceWorkerContextClient

Using switch is the best option here to get compile time verification, and
we can catch it if WebServiceWorkerEventResult gains a new type later.

Here also replace some if-return with DCHECK.

BUG=None

Review-Url: https://codereview.chromium.org/2606303002
Cr-Commit-Position: refs/heads/master@{#442822}

AUTHORS

@@ -730,6 +730,7 @@ William Xie <william.xie@chromium.com>
 William Xie <william.xie@intel.com>
 Xiang Long <xiang.long@intel.com>
 Xiangze Zhang <xiangze.zhang@intel.com>
+Xiaofeng Zhang <xiaofeng.zhang@intel.com>
 Xiaolei Yu <dreifachstein@gmail.com>
 Xiaoyin Liu <xiaoyin.l@outlook.com>
 Xinchao He <hexinchao@gmail.com>

content/renderer/service_worker/service_worker_context_client.cc

@@ -114,6 +114,18 @@ class WebServiceWorkerNetworkProviderImpl
   }
 };
 
+ServiceWorkerStatusCode EventResultToStatus(
+    blink::WebServiceWorkerEventResult result) {
+  switch (result) {
+    case blink::WebServiceWorkerEventResultCompleted:
+      return SERVICE_WORKER_OK;
+    case blink::WebServiceWorkerEventResultRejected:
+      return SERVICE_WORKER_ERROR_EVENT_WAITUNTIL_REJECTED;
+  }
+  NOTREACHED() << "Got invalid result: " << result;
+  return SERVICE_WORKER_ERROR_FAILED;
+}
+
 void SendPostMessageToClientOnMainThread(
     ThreadSafeSender* sender,
     int routing_id,
@@ -674,13 +686,8 @@ void ServiceWorkerContextClient::didHandleExtendableMessageEvent(
   const DispatchExtendableMessageEventCallback* callback =
       context_->message_event_callbacks.Lookup(request_id);
   DCHECK(callback);
-  if (result == blink::WebServiceWorkerEventResultCompleted) {
-    callback->Run(SERVICE_WORKER_OK,
-                  base::Time::FromDoubleT(event_dispatch_time));
-  } else {
-    callback->Run(SERVICE_WORKER_ERROR_EVENT_WAITUNTIL_REJECTED,
-                  base::Time::FromDoubleT(event_dispatch_time));
-  }
+  callback->Run(EventResultToStatus(result),
+                base::Time::FromDoubleT(event_dispatch_time));
   context_->message_event_callbacks.Remove(request_id);
 }
 
@@ -725,12 +732,8 @@ void ServiceWorkerContextClient::didHandleFetchEvent(
   }
   const FetchCallback* callback =
       context_->fetch_event_callbacks.Lookup(fetch_event_id);
-  if (!callback)
-    return;
-
-  callback->Run(result == blink::WebServiceWorkerEventResultCompleted
-                    ? SERVICE_WORKER_OK
-                    : SERVICE_WORKER_ERROR_EVENT_WAITUNTIL_REJECTED,
+  DCHECK(callback);
+  callback->Run(EventResultToStatus(result),
                 base::Time::FromDoubleT(event_dispatch_time));
   context_->fetch_event_callbacks.Remove(fetch_event_id);
 }
@@ -768,15 +771,9 @@ void ServiceWorkerContextClient::didHandleSyncEvent(
     double event_dispatch_time) {
   const SyncCallback* callback =
       context_->sync_event_callbacks.Lookup(request_id);
-  if (!callback)
-    return;
-  if (result == blink::WebServiceWorkerEventResultCompleted) {
-    callback->Run(SERVICE_WORKER_OK,
-                  base::Time::FromDoubleT(event_dispatch_time));
-  } else {
-    callback->Run(SERVICE_WORKER_ERROR_EVENT_WAITUNTIL_REJECTED,
-                  base::Time::FromDoubleT(event_dispatch_time));
-  }
+  DCHECK(callback);
+  callback->Run(EventResultToStatus(result),
+                base::Time::FromDoubleT(event_dispatch_time));
   context_->sync_event_callbacks.Remove(request_id);
 }