Cache user agent string in FrameLoaderClientImpl instead of BlinkPlatformImpl

third_party/WebKit/Source/web/FrameLoaderClientImpl.h

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 174 matching lines @@
     PassOwnPtrWillBeRawPtr<LinkResource> createServiceWorkerLinkResource(HTMLLinkElement*) override;
 
 private:
     explicit FrameLoaderClientImpl(WebLocalFrameImpl*);
 
     bool isFrameLoaderClientImpl() const override { return true; }
 
     // The WebFrame that owns this object and manages its lifetime. Therefore,
     // the web frame object is guaranteed to exist.
     RawPtrWillBeMember<WebLocalFrameImpl> m_webFrame;
+
+    String m_userAgent;
 };
 
 DEFINE_TYPE_CASTS(FrameLoaderClientImpl, FrameLoaderClient, client, client->isFrameLoaderClientImpl(), client.isFrameLoaderClientImpl());
 
 } // namespace blink
 
 #endif