Expose Document::isPrivilegedContext from WebDocument

Source/web/WebDocument.cpp

Index: Source/web/WebDocument.cpp
diff --git a/Source/web/WebDocument.cpp b/Source/web/WebDocument.cpp
index 1cfc8aebb9ab90835b1d357ad7cae1318aba3c46..1ae13e3e8f8623d3607e95cbaab8e615b07ecdb8 100644
--- a/Source/web/WebDocument.cpp
+++ b/Source/web/WebDocument.cpp
@@ -82,6 +82,17 @@ WebSecurityOrigin WebDocument::securityOrigin() const
     return WebSecurityOrigin(constUnwrap<Document>()->securityOrigin());
 }
 
+bool WebDocument::isPrivilegedContext(WebString& errorMessage)
+{
+    Document* document = unwrap<Document>();

[jww, 2015/05/12 02:35:20]

I *think* isPrivilegedContext() actually could be made const, and then the
unwrap could be made a constUnwrap(). If you're feeling generous, you might
consider making that change, but it's also not necessary.

+    if (!document)
+        return false;
+    String message;
+    bool result = document->isPrivilegedContext(message);
+    errorMessage = message;
+    return result;
+}
+
 WebString WebDocument::encoding() const
 {
     return constUnwrap<Document>()->encodingName();