Cache User Agent string in BlinkPlatformImpl

content/child/blink_platform_impl.cc

 // 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 "content/child/blink_platform_impl.h"
 
 #include <math.h>
 
 #include <vector>
 
@@ skipping 469 matching lines @@
       child_thread ? child_thread->resource_dispatcher() : NULL,
       make_scoped_ptr(new scheduler::WebTaskRunnerImpl(
             base::ThreadTaskRunnerHandle::Get())));
 }
 
 blink::WebSocketHandle* BlinkPlatformImpl::createWebSocketHandle() {
   return new WebSocketBridge;
 }
 
 WebString BlinkPlatformImpl::userAgent() {
-  return WebString::fromUTF8(GetContentClient()->GetUserAgent());
+  CR_DEFINE_STATIC_LOCAL(
+      blink::WebString, user_agent,
+      (blink::WebString::fromUTF8(GetContentClient()->GetUserAgent())));
+  DCHECK(user_agent ==
+         blink::WebString::fromUTF8(GetContentClient()->GetUserAgent()));
+  return user_agent;
 }
 
 WebData BlinkPlatformImpl::parseDataURL(const WebURL& url,
                                         WebString& mimetype_out,
                                         WebString& charset_out) {
   std::string mime_type, char_set, data;
   if (net::DataURL::Parse(url, &mime_type, &char_set, &data) &&
       mime_util::IsSupportedMimeType(mime_type)) {
     mimetype_out = WebString::fromUTF8(mime_type);
     charset_out = WebString::fromUTF8(char_set);
@@ skipping 819 matching lines @@
   return WebString::fromUTF8(ui::KeycodeConverter::DomKeyToKeyString(
       static_cast<ui::DomKey>(dom_key)));
 }
 
 int BlinkPlatformImpl::domKeyEnumFromString(const WebString& key_string) {
   return static_cast<int>(
       ui::KeycodeConverter::KeyStringToDomKey(key_string.utf8()));
 }
 
 }  // namespace content