Cache User Agent string in BlinkPlatformImpl

third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp

 /*
  * 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 668 matching lines @@
         m_webFrame->client()->didCreateDataSource(m_webFrame, ds.get());
     return ds.release();
 }
 
 String FrameLoaderClientImpl::userAgent()
 {
     WebString override = m_webFrame->client()->userAgentOverride(m_webFrame);
     if (!override.isEmpty())
         return override;
 
-    return Platform::current()->userAgent();
+    if (m_userAgent.isNull())
+        m_userAgent = Platform::current()->userAgent();

[kinuko, 2015/10/16 11:12:21]

Maybe add a comment in Platform.h to note that the return value of userAgent()
is not expected to be changed and can be cached.

[tzik, 2015/10/19 08:16:48]

Done.

+    return m_userAgent;
 }
 
 String FrameLoaderClientImpl::doNotTrackValue()
 {
     WebString doNotTrack = m_webFrame->client()->doNotTrackValue(m_webFrame);
     if (!doNotTrack.isEmpty())
         return doNotTrack;
     return String();
 }
 
@@ skipping 256 matching lines @@
 
 void FrameLoaderClientImpl::suddenTerminationDisablerChanged(bool present, SuddenTerminationDisablerType type)
 {
     if (m_webFrame->client()) {
         m_webFrame->client()->suddenTerminationDisablerChanged(
             present, static_cast<WebFrameClient::SuddenTerminationDisablerType>(type));
     }
 }
 
 } // namespace blink