Add WebDocument::manifestURL().

Source/web/WebDocument.cpp

Index: Source/web/WebDocument.cpp
diff --git a/Source/web/WebDocument.cpp b/Source/web/WebDocument.cpp
index 987d16993d96180a80fb1939f42c38ab4fa75014..37b3a60861b601fa31ba0e3b8fda4a1f0e57c28e 100644
--- a/Source/web/WebDocument.cpp
+++ b/Source/web/WebDocument.cpp
@@ -49,6 +49,7 @@
 #include "core/html/HTMLElement.h"
 #include "core/html/HTMLFormElement.h"
 #include "core/html/HTMLHeadElement.h"
+#include "core/html/HTMLLinkElement.h"
 #include "core/loader/DocumentLoader.h"
 #include "core/rendering/RenderObject.h"
 #include "core/rendering/RenderView.h"
@@ -336,6 +337,15 @@ v8::Handle<v8::Value> WebDocument::registerEmbedderCustomElement(const WebString
     return constructor.v8Value();
 }
 
+WebURL WebDocument::manifestURL() const
+{
+    const Document* document = constUnwrap<Document>();
+    HTMLLinkElement* linkElement = document->linkManifest();
+    if (!linkElement)
+        return WebURL();
+    return linkElement->href();
+}
+
 WebDocument::WebDocument(const PassRefPtrWillBeRawPtr<Document>& elem)
     : WebNode(elem)
 {