Expose %ErrorPrototype% as an intrinsic in the public API.

Blink needs %ErrorPrototype% in order to properly set up the inheritance
chain from DOMException, as specified in WebIDL:
https://heycam.github.io/webidl/#es-DOMException-specialness

This patch is similar to commit 5ec1cddc ("Expose %IteratorPrototype% as an
intrinsic in the public API"), with the difference that there was no entry
for %ErrorPrototype% in any of the mappings in contexts.h.

Bug: chromium:556950, chromium:737497
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Iadc5b2b844f29f6c9640b6a89769d233931366e9
Reviewed-on: https://chromium-review.googlesource.com/559058Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Raphael Kubo da Costa (rakuco) <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#46464}

include/v8.h

@@ -4921,6 +4921,7 @@ class V8_EXPORT External : public Value {
   F(ArrayProto_forEach, array_for_each_iterator) \
   F(ArrayProto_keys, array_keys_iterator)        \
   F(ArrayProto_values, array_values_iterator)    \
+  F(ErrorPrototype, initial_error_prototype)     \
   F(IteratorPrototype, initial_iterator_prototype)
 
 enum Intrinsic {

src/bootstrapper.cc

@@ -1170,6 +1170,7 @@ static void InstallError(Isolate* isolate, Handle<JSObject> global,
           SimpleInstallFunction(prototype, factory->toString_string(),
                                 Builtins::kErrorPrototypeToString, 0, true);
       isolate->native_context()->set_error_to_string(*to_string_fun);
+      isolate->native_context()->set_initial_error_prototype(*prototype);
     } else {
       DCHECK(isolate->native_context()->error_to_string()->IsJSFunction());
 

src/contexts.h

@@ -254,6 +254,7 @@ enum ContextLookupFlags {
   V(INITIAL_ARRAY_ITERATOR_PROTOTYPE_MAP_INDEX, Map,                           \
     initial_array_iterator_prototype_map)                                      \
   V(INITIAL_ARRAY_PROTOTYPE_INDEX, JSObject, initial_array_prototype)          \
+  V(INITIAL_ERROR_PROTOTYPE_INDEX, JSObject, initial_error_prototype)          \
   V(INITIAL_GENERATOR_PROTOTYPE_INDEX, JSObject, initial_generator_prototype)  \
   V(INITIAL_ASYNC_GENERATOR_PROTOTYPE_INDEX, JSObject,                         \
     initial_async_generator_prototype)                                         \

test/cctest/test-api.cc

@@ -26215,6 +26215,76 @@ TEST(TemplateIteratorPrototypeIntrinsics) {
   }
 }
 
+TEST(TemplateErrorPrototypeIntrinsics) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope scope(isolate);
+  LocalContext env;
+
+  // Object templates.
+  {
+    Local<ObjectTemplate> object_template = v8::ObjectTemplate::New(isolate);
+    object_template->SetIntrinsicDataProperty(v8_str("error_proto"),
+                                              v8::kErrorPrototype);
+    Local<Object> object =
+        object_template->NewInstance(env.local()).ToLocalChecked();
+    CHECK(env->Global()->Set(env.local(), v8_str("obj"), object).FromJust());
+    ExpectTrue("obj.error_proto === Error.prototype");
+    Local<Value> error = v8::Exception::Error(v8_str("error message"));
+    CHECK(env->Global()->Set(env.local(), v8_str("err"), error).FromJust());
+    ExpectTrue("obj.error_proto === Object.getPrototypeOf(err)");
+  }
+  // Setting %ErrorPrototype% on the function object's prototype template.
+  {
+    Local<FunctionTemplate> func_template = v8::FunctionTemplate::New(isolate);
+    func_template->PrototypeTemplate()->SetIntrinsicDataProperty(
+        v8_str("error_proto"), v8::kErrorPrototype);
+    Local<Function> func1 =
+        func_template->GetFunction(env.local()).ToLocalChecked();
+    CHECK(env->Global()->Set(env.local(), v8_str("func1"), func1).FromJust());
+    Local<Function> func2 =
+        func_template->GetFunction(env.local()).ToLocalChecked();
+    CHECK(env->Global()->Set(env.local(), v8_str("func2"), func2).FromJust());
+    ExpectTrue("func1.prototype.error_proto === Error.prototype");
+    ExpectTrue("func2.prototype.error_proto === Error.prototype");
+    ExpectTrue("func1.prototype.error_proto === func2.prototype.error_proto");
+
+    Local<Object> instance1 = func1->NewInstance(env.local()).ToLocalChecked();
+    CHECK(env->Global()
+              ->Set(env.local(), v8_str("instance1"), instance1)
+              .FromJust());
+    ExpectFalse("instance1.hasOwnProperty('error_proto')");
+    ExpectTrue("'error_proto' in instance1.__proto__");
+    ExpectTrue("instance1.error_proto === Error.prototype");
+  }
+  // Put %ErrorPrototype% in a function object's inheritance chain.
+  {
+    Local<FunctionTemplate> parent_template =
+        v8::FunctionTemplate::New(isolate);
+    parent_template->RemovePrototype();  // Remove so there is no name clash.
+    parent_template->SetIntrinsicDataProperty(v8_str("prototype"),
+                                              v8::kErrorPrototype);
+    Local<FunctionTemplate> func_template = v8::FunctionTemplate::New(isolate);
+    func_template->Inherit(parent_template);
+
+    Local<Function> func =
+        func_template->GetFunction(env.local()).ToLocalChecked();
+    CHECK(env->Global()->Set(env.local(), v8_str("func"), func).FromJust());
+    ExpectTrue("func.prototype.__proto__ === Error.prototype");
+
+    Local<Object> func_instance =
+        func->NewInstance(env.local()).ToLocalChecked();
+    CHECK(env->Global()
+              ->Set(env.local(), v8_str("instance"), func_instance)
+              .FromJust());
+    ExpectTrue("instance.__proto__.__proto__.__proto__ === Object.prototype");
+    // Now let's check if %ErrorPrototype% properties are in the instance.
+    ExpectTrue("'constructor' in instance");
+    ExpectTrue("'message' in instance");
+    ExpectTrue("'name' in instance");
+    ExpectTrue("'toString' in instance");
+  }
+}
+
 TEST(ObjectTemplateArrayProtoIntrinsics) {
   v8::Isolate* isolate = CcTest::isolate();
   v8::HandleScope scope(isolate);