[proxies] Better print for proxies in d8

src/d8.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 "use strict";
 
 // A more universal stringify that supports more types than JSON.
 // Used by the d8 shell to output results.
 var stringifyDepthLimit = 4;  // To avoid crashing on cyclic objects
 
 function Stringify(x, depth) {
   if (depth === undefined)
     depth = stringifyDepthLimit;
   else if (depth === 0)
     return "*";
+  if (IS_PROXY(x)) {
+    return StringifyProxy(x, depth);
+  }
   switch (typeof x) {
     case "undefined":
       return "undefined";
     case "boolean":
     case "number":
     case "function":
       return x.toString();
     case "string":
       return "\"" + x.toString() + "\"";
     case "symbol":
@@ skipping 30 matching lines @@
         if (desc.set) {
           var setter = Stringify(desc.set);
           props.push("set " + name + setter.slice(setter.indexOf('(')));
         }
       }
       return "{" + props.join(", ") + "}";
     default:
       return "[crazy non-standard value]";
   }
 }
+
+function StringifyProxy(proxy, depth) {
+  var proxy_type = typeof proxy;
+  return '[' + proxy_type + ' Proxy {' +
+    'target: ' +
+        StringifyProxyInternal(%JSProxyGetTarget(proxy), depth) + ', ' +
+    'handler: '+
+        StringifyProxyInternal(%JSProxyGetHandler(proxy), depth) +
+  '}]';
+}
+
+function StringifyProxyInternal(object, depth) {
+  // Special case to handle proxy __proto__ recursions on target or handler.
+  try {
+    return Stringify(object, depth-1);
+  } catch(RangeError) {
+    return '{*}'
+  }
+}