Make instanceof and Object.getPrototypeOf work for proxies, plus a few other tweaks.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 4997d56df54b8dceb95b98938b0bff0dca4283d7..08acfd120b5caf11b9bd1d249cbabfa328d4f374 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -594,12 +594,26 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateJSProxy) {
   Object* handler = args[0];
   Object* prototype = args[1];
   Object* used_prototype =
-      (prototype->IsJSObject() || prototype->IsJSProxy()) ? prototype
-          : isolate->heap()->null_value();
+      prototype->IsJSReceiver() ? prototype : isolate->heap()->null_value();
   return isolate->heap()->AllocateJSProxy(handler, used_prototype);
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_IsJSProxy) {
+  ASSERT(args.length() == 1);
+  Object* obj = args[0];
+  return obj->IsJSProxy()
+      ? isolate->heap()->true_value() : isolate->heap()->false_value();
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_GetHandler) {
+  ASSERT(args.length() == 1);
+  CONVERT_CHECKED(JSProxy, proxy, args[0]);
+  return proxy->handler();
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateCatchExtensionObject) {
   ASSERT(args.length() == 2);
   CONVERT_CHECKED(String, key, args[0]);
@@ -634,6 +648,15 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_ClassOf) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_GetPrototype) {
+  NoHandleAllocation ha;
+  ASSERT(args.length() == 1);
+  Object* obj = args[0];
+  if (obj->IsJSGlobalProxy()) obj = obj->GetPrototype();
+  return obj->GetPrototype();
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_IsInPrototypeChain) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);