[proxy] fixing harmony/proxy.js tests and improving error messages + some drive-by fixes

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index ed44793e0714d31056049310e7e47a334ab95fbe..b2bcd9ecd01cc5d59468d7c891862b1ccbbc40bb 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -774,7 +774,8 @@ bool Isolate::IsInternallyUsedPropertyName(Handle<Object> name) {
 
 bool Isolate::MayAccess(Handle<Context> accessing_context,
                         Handle<JSObject> receiver) {
-  DCHECK(receiver->IsJSGlobalProxy() || receiver->IsAccessCheckNeeded());
+  DCHECK(receiver->IsJSGlobalProxy() || receiver->IsJSGlobalObject() ||
+         receiver->IsAccessCheckNeeded());
 
   // Check for compatibility between the security tokens in the
   // current lexical context and the accessed object.
@@ -801,6 +802,28 @@ bool Isolate::MayAccess(Handle<Context> accessing_context,
     }
   }
 
+  {
+    DisallowHeapAllocation no_gc;
+    // During bootstrapping, callback functions are not enabled yet.
+    if (bootstrapper()->IsActive()) return true;
+
+    if (receiver->IsJSGlobalObject()) {
+      Object* receiver_context =
+          JSGlobalObject::cast(*receiver)->native_context();
+      if (!receiver_context->IsContext()) return false;
+
+      // Get the native context of current top context.
+      // avoid using Isolate::native_context() because it uses Handle.
+      Context* native_context =
+          accessing_context->global_object()->native_context();
+      if (receiver_context == native_context) return true;
+
+      if (Context::cast(receiver_context)->security_token() ==
+          native_context->security_token())
+        return true;
+    }
+  }
+
   HandleScope scope(this);
   Handle<Object> data;
   v8::AccessCheckCallback callback = nullptr;