Set default document urls to 'about:blank'.

third_party/WebKit/Source/core/dom/Document.h

Index: third_party/WebKit/Source/core/dom/Document.h
diff --git a/third_party/WebKit/Source/core/dom/Document.h b/third_party/WebKit/Source/core/dom/Document.h
index 83ac39074f9b1e2d498b3f827d279ed4c99de0c0..a96d14e8b2663a4cc816efcef9e84012ca6c020c 100644
--- a/third_party/WebKit/Source/core/dom/Document.h
+++ b/third_party/WebKit/Source/core/dom/Document.h
@@ -593,9 +593,14 @@ class CORE_EXPORT Document : public ContainerNode,
 
   bool wellFormed() const { return m_wellFormed; }
 
+  // Return the document URL, or an empty URL if it's unavailable.
+  // This is not an implementation of web-exposed Document.prototype.URL.
   const KURL& url() const { return m_url; }
   void setURL(const KURL&);
 
+  // Bind the url to document.url, if unavailable bind to about:blank.
+  KURL urlForBinding();
+
   // To understand how these concepts relate to one another, please see the
   // comments surrounding their declaration.
   const KURL& baseURL() const { return m_baseURL; }