Restore a document.isActive() check to fix perf regression

Source/core/loader/ImageLoader.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 157 matching lines @@
 {
     // We don't need to call clearLoader here: Either we were called from the
     // task, or our caller updateFromElement cleared the task's loader (and set
     // m_pendingTask to null).
     m_pendingTask.clear();
     // Make sure to only decrement the count when we exit this function
     OwnPtr<IncrementLoadEventDelayCount> delayLoad;
     delayLoad.swap(m_delayLoad);
 
     Document& document = m_element->document();
+    if (!document.isActive())
+        return;
 
     AtomicString attr = m_element->imageSourceURL();
 
     KURL url = imageURL();
     ResourcePtr<ImageResource> newImage = 0;
     if (!url.isNull()) {
         FetchRequest request(ResourceRequest(url), element()->localName());
         if (bypassMainWorldCSP)
             request.setContentSecurityCheck(DoNotCheckContentSecurityPolicy);
 
@@ skipping 351 matching lines @@
 }
 
 #if ENABLE(OILPAN)
 ImageLoader::ImageLoaderClientRemover::~ImageLoaderClientRemover()
 {
     m_loader.willRemoveClient(m_client);
 }
 #endif
 
 }