Throw JavaScript error instead of CHECK when this in privates is invalid

extensions/renderer/module_system.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/renderer/module_system.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/stl_util.h"
@@ skipping 545 matching lines @@
       "console, privates,"
       "$Array, $Function, $JSON, $Object, $RegExp, $String, $Error) {"
       "'use strict';");
   v8::Handle<v8::String> right = v8::String::NewFromUtf8(GetIsolate(), "\n})");
   return handle_scope.Escape(v8::Local<v8::String>(
       v8::String::Concat(left, v8::String::Concat(source, right))));
 }
 
 void ModuleSystem::Private(const v8::FunctionCallbackInfo<v8::Value>& args) {
   CHECK_EQ(1, args.Length());
-  CHECK(args[0]->IsObject());
-  CHECK(!args[0]->IsNull());
+  if (!args[0]->IsObject() || args[0]->IsNull()) {
+    GetIsolate()->ThrowException(
+        v8::Exception::TypeError(v8::String::NewFromUtf8(GetIsolate(),
+            args[0]->IsUndefined()
+                ? "Method called without a valid receiver (this). "
+                  "Did you forget to call .bind()?"
+                : "Invalid invocation: receiver is not an object!")));
+    return;
+  }
   v8::Local<v8::Object> obj = args[0].As<v8::Object>();
   v8::Local<v8::String> privates_key =
       v8::String::NewFromUtf8(GetIsolate(), "privates");
   v8::Local<v8::Value> privates = obj->GetHiddenValue(privates_key);
   if (privates.IsEmpty()) {
     privates = v8::Object::New(args.GetIsolate());
     if (privates.IsEmpty()) {
       GetIsolate()->ThrowException(
           v8::String::NewFromUtf8(GetIsolate(), "Failed to create privates"));
       return;
@@ skipping 92 matching lines @@
     v8::Handle<v8::Value> value) {
   if (!is_valid())
     return;
   v8::HandleScope handle_scope(GetIsolate());
   v8::Handle<v8::Promise::Resolver> resolver_local(
       v8::Local<v8::Promise::Resolver>::New(GetIsolate(), *resolver));
   resolver_local->Resolve(value);
 }
 
 }  // namespace extensions