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 2ccf57b16874d11cd03de99aa78d1f781b17d22f..197f3e20cbd7d85963a83ad3011a8950065963da 100644
--- a/Source/core/loader/cache/CachedResource.cpp
+++ b/Source/core/loader/cache/CachedResource.cpp
@@ -193,7 +193,7 @@ 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;