Have Node::document() return a reference instead of a pointer

Source/core/loader/DocumentLoader.cpp

Index: Source/core/loader/DocumentLoader.cpp
diff --git a/Source/core/loader/DocumentLoader.cpp b/Source/core/loader/DocumentLoader.cpp
index f96cae29d9e2f9d27ba61d53e63f30b1be46a349..194552ea576096fca7358e2ecd122c3d7ad6688d 100644
--- a/Source/core/loader/DocumentLoader.cpp
+++ b/Source/core/loader/DocumentLoader.cpp
@@ -395,7 +395,7 @@ bool DocumentLoader::shouldContinueForNavigationPolicy(const ResourceRequest& re
 
     // If we're loading content into a subframe, check against the parent's Content Security Policy
     // and kill the load if that check fails.
-    if (m_frame->ownerElement() && !m_frame->ownerElement()->document()->contentSecurityPolicy()->allowChildFrameFromSource(request.url()))
+    if (m_frame->ownerElement() && !m_frame->ownerElement()->document().contentSecurityPolicy()->allowChildFrameFromSource(request.url()))
         return false;
 
     NavigationPolicy policy = NavigationPolicyCurrentTab;