Refactoring: Introduce ResouceLoaderHost interface for unloading ResourceLoader.

Source/core/loader/cache/CachedResource.cpp

Index: Source/core/loader/cache/CachedResource.cpp
diff --git a/Source/core/loader/cache/CachedResource.cpp b/Source/core/loader/cache/CachedResource.cpp
index ef7be1112b5d0cb1c5318b26cfa8e9c94b93c404..3a070bea120d52ff9880d100dc068ea04a043dc6 100644
--- a/Source/core/loader/cache/CachedResource.cpp
+++ b/Source/core/loader/cache/CachedResource.cpp
@@ -181,7 +181,7 @@ void CachedResource::load(CachedResourceLoader* cachedResourceLoader, const Reso
         m_fragmentIdentifierForRequest = String();
     }
 
-    m_loader = ResourceLoader::create(cachedResourceLoader->documentLoader(), this, request, options);
+    m_loader = ResourceLoader::create(cachedResourceLoader, this, request, options);
     if (!m_loader) {
         failBeforeStarting();
         return;