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

third_party/WebKit/public/web/WebDataSource.h

Index: third_party/WebKit/public/web/WebDataSource.h
diff --git a/third_party/WebKit/public/web/WebDataSource.h b/third_party/WebKit/public/web/WebDataSource.h
index d9e72b3e0a25c8037fa7f93c717c9bb41a5cb559..3efdaf6eb7214fc3b49bda4b3a6ef6fa172e6b86 100644
--- a/third_party/WebKit/public/web/WebDataSource.h
+++ b/third_party/WebKit/public/web/WebDataSource.h
@@ -33,7 +33,6 @@
 
 #include "../platform/WebCommon.h"
 #include "WebNavigationType.h"
-#include "WebTextDirection.h"
 
 namespace blink {
 
@@ -51,6 +50,10 @@ class WebDataSource {
     virtual ~ExtraData() {}
   };
 
+  // Returns the URL of the document that triggered the creation of this
+  // datasource. Will return an empty URL once this datasource commits.

[dcheng, 2016/11/23 08:32:59]

Unfortunately, I realized that the previous implementation would keep Documents
live indefinitely. So I changed it to a more complex interface =(

+  virtual WebURL requestorURL() const = 0;
+
   // Returns the original request that resulted in this datasource.
   virtual const WebURLRequest& originalRequest() const = 0;