Expose the initiating origin/URL of a navigation in the Blink public API

third_party/WebKit/Source/core/loader/DocumentLoader.h

Index: third_party/WebKit/Source/core/loader/DocumentLoader.h
diff --git a/third_party/WebKit/Source/core/loader/DocumentLoader.h b/third_party/WebKit/Source/core/loader/DocumentLoader.h
index 21af660142a3493b92cd39e5a1f50910b72cedba..b908aae09d7bb2340af7e55d4379c069edc9daf9 100644
--- a/third_party/WebKit/Source/core/loader/DocumentLoader.h
+++ b/third_party/WebKit/Source/core/loader/DocumentLoader.h
@@ -72,8 +72,10 @@ class CORE_EXPORT DocumentLoader
   static DocumentLoader* create(LocalFrame* frame,
                                 const ResourceRequest& request,
                                 const SubstituteData& data,
-                                ClientRedirectPolicy clientRedirectPolicy) {
-    return new DocumentLoader(frame, request, data, clientRedirectPolicy);
+                                ClientRedirectPolicy clientRedirectPolicy,
+                                Document* requestorDocument) {
+    return new DocumentLoader(frame, request, data, clientRedirectPolicy,
+                              requestorDocument);
   }
   ~DocumentLoader() override;
 
@@ -188,7 +190,10 @@ class CORE_EXPORT DocumentLoader
   DocumentLoader(LocalFrame*,
                  const ResourceRequest&,
                  const SubstituteData&,
-                 ClientRedirectPolicy);
+                 ClientRedirectPolicy,
+                 Document* requestorDocument);
+
+  Document* requestorDocument() const { return m_requestorDocument; }
 
   void didRedirect(const KURL& oldURL, const KURL& newURL);
 
@@ -241,6 +246,8 @@ class CORE_EXPORT DocumentLoader
 
   Member<DocumentWriter> m_writer;
 
+  Member<Document> m_requestorDocument;
+
   // A reference to actual request used to create the data source.
   // The only part of this request that should change is the url, and
   // that only in the case of a same-document navigation.