Bug 1063247: Allow implicit construction of JS::ubi::Node from JS::HandleValue. r=terrence

This seems reasonable, since a ubi::Node is really just a pointer with some
introspection support, so the value and the Node are pretty similar. And I don't
see cases where you'd want an error.

js/public/UbiNode.h

@@ -271,7 +271,7 @@ class Node {
     }
 
     // Constructors accepting SpiderMonkey's other generic-pointer-ish types.
-    explicit Node(JS::Value value);
+    Node(JS::HandleValue value);
     Node(JSGCTraceKind kind, void *ptr);
 
     // copy construction and copy assignment just use memcpy, since we know

js/src/vm/UbiNode.cpp

@@ -60,7 +60,7 @@ Node::Node(JSGCTraceKind kind, void *ptr)
     }
 }
 
-Node::Node(Value value)
+Node::Node(HandleValue value)
 {
     if (value.isObject())
         construct(&value.toObject());