Use the single char overload of append() when possible.

third_party/WebKit/Source/modules/cachestorage/InspectorCacheStorageAgent.cpp

 // Copyright 2014 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/cachestorage/InspectorCacheStorageAgent.h"
 
 #include "platform/heap/Handle.h"
 #include "platform/inspector_protocol/DispatcherBase.h"
 #include "platform/inspector_protocol/Values.h"
 #include "platform/weborigin/KURL.h"
@@ skipping 28 matching lines @@
 typedef blink::protocol::CacheStorage::Backend::RequestEntriesCallback RequestEntriesCallback;
 typedef blink::WebServiceWorkerCache::BatchOperation BatchOperation;
 
 namespace blink {
 
 namespace {
 
 String buildCacheId(const String& securityOrigin, const String& cacheName)
 {
     String id(securityOrigin);
-    id.append("|");
+    id.append('|');
     id.append(cacheName);
     return id;
 }
 
 bool parseCacheId(ErrorString* errorString, const String& id, String* securityOrigin, String* cacheName)
 {
     size_t pipe = id.find('|');
     if (pipe == WTF::kNotFound) {
         *errorString = "Invalid cache id.";
         return false;
@@ skipping 397 matching lines @@
     std::unique_ptr<WebServiceWorkerCacheStorage> cache = assertCacheStorageAndNameForId(errorString, cacheId, &cacheName);
     if (!cache) {
         callback->sendFailure(*errorString);
         return;
     }
     cache->dispatchOpen(new GetCacheForDeleteEntry(request, cacheName, std::move(callback)), WebString(cacheName));
 }
 
 
 } // namespace blink