Support new style JS interop

Source/bindings/core/dart/DartJsInterop.cpp

Index: Source/bindings/core/dart/DartJsInterop.cpp
diff --git a/Source/bindings/core/dart/DartJsInterop.cpp b/Source/bindings/core/dart/DartJsInterop.cpp
index 4ac046c4c6680d2598e5e426486c68b22dc3f673..af37d6419a74c8b35930e317d3d64d6a3fd85910 100644
--- a/Source/bindings/core/dart/DartJsInterop.cpp
+++ b/Source/bindings/core/dart/DartJsInterop.cpp
@@ -52,8 +52,93 @@ const int JsObject::dartClassId = _JsObjectClassId;
 const int JsFunction::dartClassId = _JsFunctionClassId;
 const int JsArray::dartClassId = _JsArrayClassId;
 
+// TODO(jacobr): v8::String::NewFromUtf8 usages should be cached for constant
+// strings to improve performance.
+/**
+ * Polyfill script to make Dart List objects look like JavaScript arrays when
+ * passed to JavaScript via JavaScript interop. Handling the edge cases
+ * requires patching the JavaScript Array prototype for a couple methods
+ * and implementing all of the JavaScript Array methods on the JavaScript
+ * proxy object for the Dart List. Some of the JavaScript methods are
+ * implemented in Dart and C++ code, some are implemented in this JavaScript
+ * polyfill script.
+ */
+const char* dartArrayPolyfill =
+    "(function() {"
+    // If filter has already been defined on the DartList prototype,
+    // another DOM isolate has beaten us to polyfilling.
+    "  if ($DartList.prototype.hasOwnProperty('filter')) return;"
+    "  var isArray = Array.isArray;"
+    "  var concat = Array.prototype.concat;"
+    "  function makeSafeArgs(args) {"
+    "    var len = args.length;"
+    "    for (var i = 0; i < len; ++i) {"
+    "      var arg = args[i];"
+    "      if (arg instanceof $DartList) {"
+    "       args[i] = arg.$toJsArray();"
+    "      }"
+    "    }"
+    "  };"
+
+    // If performance becomes an issue, we could implement these
+    // methods in Dart instead of creating a shallow copy JavaScript
+    // array containing the elements of the Dart List and calling
+    // the JavaScript method.
+
+    // Handle methods that take a callback with value, index, and thisArg
+    // parameters. The trick is we need to make thisArg reference the
+    // underlying Dart List rather than the JavaScript copy we create for
+    // implementation convenience.
+    "  ['filter', 'forEach', 'some', 'every', 'map'].forEach(function(name) {"
+    "    Object.defineProperty($DartList.prototype, name, {enumerable: false, value: function(callback, thisArg) {"
+    "      var dartList = this;"
+    "      return this.$toJsArray()[name](function(value, index) {"
+    "          return callback.call(thisArg, value, index, dartList);"
+    "      });"
+    "    }});"
+    "  });"
+
+    "  ['slice', 'indexOf', 'lastIndexOf'].forEach(function(name) {"
+    "    Object.defineProperty($DartList.prototype, name, {enumerable: false, value: function() {"
+    "      var jsArray = this.$toJsArray();"
+    "      return jsArray[name].apply(jsArray, arguments);"
+    "    }});"
+    "  });"
+
+    "  ['reduce', 'reduceRight'].forEach(function(name) {"
+    "    Object.defineProperty($DartList.prototype, name, {enumerable: false, value: function(callback, thisArg) {"
+    "      var dartList = this;"
+    "      return this.$toJsArray()[name](function(previousValue, currentValue, index) {"
+    "          return callback.call(thisArg, previousValue, currentValue, index, dartList);"
+    "      });"
+    "    }});"
+    "  });"
+
+    // Arguments to concat that are Arrays are treated differently.
+    // Warning: this will slow down general JavaScript array concat performance in Dartium.
+    "  Array.prototype.concat = function() {"
+    "    makeSafeArgs(arguments);"
+    "    return concat.apply(this, arguments);"
+    "  };"
+
+    // Need to make sure that Array.isArray returns true for Dart lists.
+    "  Array.isArray = function(arr) {"
+    "    return isArray(arr) || (arr instanceof $DartList);"
+    "  };"
+    "})();";
+
 static v8::Local<v8::FunctionTemplate> dartFunctionTemplate();
 static v8::Local<v8::FunctionTemplate> dartObjectTemplate();
+static v8::Local<v8::FunctionTemplate> dartListTemplate();
+
+// TODO(jacobr): we should really be using this method everywhere instead of
+// sticking interop methods in the dart:html _Utils class.
+static Dart_Handle invokeTopLevelJsInteropMethod(DartDOMData* domData, const char* methodName, int argCount, Dart_Handle* args)
+{
+    Dart_PersistentHandle library = domData->jsLibrary();
+    ASSERT(!Dart_IsError(library));
+    return Dart_Invoke(library, Dart_NewStringFromCString(methodName), argCount, args);
+}
 
 template<typename CallbackInfo>
 void setJsReturnValue(DartDOMData* domData, CallbackInfo info, Dart_Handle result)
@@ -230,7 +315,18 @@ v8::Local<v8::Value> JsInterop::fromDart(DartDOMData* domData, Dart_Handle handl
 
     v8::Local<v8::Object> proxy;
     ASSERT(Dart_IsInstance(handle));
-    proxy = dartObjectTemplate()->InstanceTemplate()->NewInstance();
+    // Simulate the behavior of the Dart dev compiler where new List() is
+    // equivalent to a JavaScript array. We accomplish this by creating a
+    // JavaScript object that fakes that it is a JavaScript array but is
+    // actually backed by a Dart list. This is not a breaking change as
+    // existing Dart-JS interop passed arrays as opaque Dart handles.
+    // The jsify method can still be called if you wish to create a copy
+    // of a json like Dart data structure.
+    if (Dart_IsList(handle)) {
+        proxy = dartListTemplate()->InstanceTemplate()->NewInstance();
+    } else {
+        proxy = dartObjectTemplate()->InstanceTemplate()->NewInstance();
+    }
     DartHandleProxy::writePointerToProxy(proxy, handle);
     v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
     proxy->SetHiddenValue(v8::String::NewFromUtf8(v8Isolate, "dartProxy"), v8::Boolean::New(v8Isolate, true));
@@ -300,9 +396,48 @@ Dart_Handle JsObject::toDart(v8::Local<v8::Object> object)
     return JsObject::toDart(jsObject);
 }
 
+static void maybeCreateJsObjectImplClass(DartDOMData* domData)
+{
+    DartJsInteropData* interopData = domData->jsInteropData();
+    // Skip if the JSObjectImpl class has already been defined.
+    if (interopData->jsObjectImplDefined()) {
+        return;
+    }
+    // Helper method that generates boilerplate source code for
+    // JsObjectImpl, JsFunctionImpl, and JsArrayImpl classes that implement
+    // all Dart types that have been passed to the dart:js registerJsInterfaces
+    // method. The sole purpose of these classes is to ensure that checked mode
+    // allows casting a JsObject to all types implemented by a JsObject.
+    Dart_Handle source = invokeTopLevelJsInteropMethod(domData, "_generateJsObjectImplPart", 0, 0);
+    ASSERT(Dart_IsString(source));
+
+    Dart_Handle ALLOW_UNUSED ret = Dart_LibraryLoadPatch(domData->jsLibrary(), Dart_NewStringFromCString("JsInteropImpl.dart"), source);
+    ASSERT(!Dart_IsError(ret));
+    ret = Dart_FinalizeLoading(false);
+    ASSERT(!Dart_IsError(ret));
+
+    interopData->setJsObjectImplDefined();
+
+    // Start of polyfill work to make Dart List proxies behave like JavaScript
+    // Arrays by monkey patching JavaScript Array and the List JavaScript
+    // proxies as needed.
+    v8::Context::Scope scope(DartUtilities::currentV8Context());
+
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
+
+    v8::Local<v8::Function> dartArrayConstructor = dartListTemplate()->GetFunction();
+
+    DartUtilities::currentV8Context()->Global()->Set(v8::String::NewFromUtf8(v8Isolate, "$DartList"),
+        dartArrayConstructor);
+    V8ScriptRunner::compileAndRunInternalScript(v8::String::NewFromUtf8(v8Isolate, dartArrayPolyfill), v8Isolate);
+}
+
 Dart_Handle JsObject::toDart(PassRefPtr<JsObject> jsObject)
 {
-    return DartDOMWrapper::createWrapper<JsObject>(DartDOMData::current(), jsObject.get(), JsObject::dartClassId);
+    DartDOMData* domData = DartDOMData::current();
+    // We need to ensure JsObjectImpl exists before creating the wrapper.
+    maybeCreateJsObjectImplClass(domData);
+    return DartDOMWrapper::createWrapper<JsObject>(domData, jsObject.get(), JsObject::dartClassId);
 }
 
 JsObject::~JsObject()
@@ -312,7 +447,10 @@ JsObject::~JsObject()
 
 Dart_Handle JsFunction::toDart(PassRefPtr<JsFunction> jsFunction)
 {
-    return DartDOMWrapper::createWrapper<JsFunction>(DartDOMData::current(), jsFunction.get(), JsFunction::dartClassId);
+    DartDOMData* domData = DartDOMData::current();
+    // We need to ensure JsObjectImpl exists before creating the wrapper.
+    maybeCreateJsObjectImplClass(domData);
+    return DartDOMWrapper::createWrapper<JsFunction>(domData, jsFunction.get(), JsFunction::dartClassId);
 }
 
 JsFunction::JsFunction(v8::Local<v8::Function> v8Handle) : JsObject(v8Handle) { }
@@ -329,7 +467,10 @@ v8::Local<v8::Function> JsFunction::localV8Function()
 
 Dart_Handle JsArray::toDart(PassRefPtr<JsArray> jsArray)
 {
-    return DartDOMWrapper::createWrapper<JsArray>(DartDOMData::current(), jsArray.get(), JsArray::dartClassId);
+    DartDOMData* domData = DartDOMData::current();
+    // We need to ensure JsArrayImpl exists before creating the wrapper.
+    maybeCreateJsObjectImplClass(domData);
+    return DartDOMWrapper::createWrapper<JsArray>(domData, jsArray.get(), JsArray::dartClassId);
 }
 
 JsArray::JsArray(v8::Local<v8::Array> v8Handle) : JsObject(v8Handle) { }
@@ -872,6 +1013,20 @@ static void contextCallback(Dart_NativeArguments args)
     Dart_SetReturnValue(args, JsObject::toDart(v8Context->Global()));
 }
 
+static void finalizeJsInterfacesCallback(Dart_NativeArguments args)
+{
+    DartDOMData* domData = static_cast<DartDOMData*>(Dart_GetNativeIsolateData(args));
+    maybeCreateJsObjectImplClass(domData);
+}
+
+static void interfacesFinalizedCallback(Dart_NativeArguments args)
+{
+    DartDOMData* domData = static_cast<DartDOMData*>(Dart_GetNativeIsolateData(args));
+    DartJsInteropData* interopData = domData->jsInteropData();
+    // Skip if the JSObjectImpl class has already been defined.
+    Dart_SetBooleanReturnValue(args, interopData->jsObjectImplDefined());
+}
+
 v8::Handle<v8::Value> mapToV8(DartDOMData* domData, Dart_Handle value, DartHandleToV8Map& map, Dart_Handle& exception)
 {
     Dart_Handle asList = DartUtilities::invokeUtilsMethod("convertMapToList", 1, &value);
@@ -1010,6 +1165,8 @@ fail:
 static DartNativeEntry nativeEntries[] = {
     { JsInteropInternal::jsObjectConstructorCallback, 2, "JsObject_constructorCallback" },
     { JsInteropInternal::contextCallback, 0, "Js_context_Callback" },
+    { JsInteropInternal::finalizeJsInterfacesCallback, 0, "Js_finalizeJsInterfaces" },
+    { JsInteropInternal::interfacesFinalizedCallback, 0, "Js_interfacesFinalized_Callback" },
     { JsInteropInternal::jsifyCallback, 1, "JsObject_jsify" },
     { JsInteropInternal::withThisCallback, 1, "JsFunction_withThis" },
     { JsInteropInternal::getterCallback, 2, "JsObject_[]" },
@@ -1055,4 +1212,331 @@ const uint8_t* JsInterop::symbolizer(Dart_NativeFunction nf)
     return 0;
 }
 
+// Methods enabling a Dart List to emulate a JS Array.
+static void indexedGetterArray(uint32_t index, const v8::PropertyCallbackInfo<v8::Value>& info)
+{
+    DartScopes scopes(info.Holder());
+    Dart_Handle handle = scopes.handle;
+    DartDOMData* domData = DartDOMData::current();
+    Dart_Handle ret = 0;
+    ASSERT(Dart_IsList(handle));
+    ret = Dart_ListGetAt(handle, index);
+    if (Dart_IsError(ret)) {
+        // Return undefined if the index is invalid to match JS semantics.
+        // TODO(jacobr): we should log to the console warning of bad use of a
+        // Dart List.
+        return;
+    }
+    setJsReturnValue(domData, info, ret);
+}
+
+static void indexedSetterArray(uint32_t index, v8::Local<v8::Value> value, const v8::PropertyCallbackInfo<v8::Value>& info)
+{
+    DartScopes scopes(info.Holder());
+    Dart_Handle handle = scopes.handle;
+    DartDOMData* domData = DartDOMData::current();
+
+    Dart_Handle ret = 0;
+    ASSERT(Dart_IsList(handle));
+    intptr_t length = 0;
+    ret = Dart_ListLength(handle, &length);
+    ASSERT(!Dart_IsError(ret));
+    if (index >= length) {
+        // Approximate JS semantics by filling the list with nulls if we
+        // attempt to add an element past the end of the list.
+        // TODO(jacobr): ideally we would match JS semantics exactly and fill
+        // the list with undefined.
+        Dart_Handle args[2] = { handle, DartUtilities::unsignedToDart(index + 1)};
+        ret = Dart_Invoke(domData->jsLibrary(), Dart_NewStringFromCString("_arrayExtend"), 2, args);
+        ASSERT(!Dart_IsError(ret));
+    }
+    ret = Dart_ListSetAt(handle, index, DartHandleProxy::unwrapValue(value));
+    if (Dart_IsError(ret)) {
+        // Return undefined if the index is invalid to match JS semantics.
+        // TODO(jacobr): we should log to the console warning of bad use of a
+        // Dart list or add a JS expando to the object ala JS.
+    }
+    setJsReturnValue(domData, info, ret);
+}
+
+static void indexedEnumeratorArray(const v8::PropertyCallbackInfo<v8::Array>& info)
+{
+    DartScopes scopes(info.Holder());
+    Dart_Handle handle = scopes.handle;
+
+    intptr_t length = 0;
+    ASSERT(Dart_IsList(handle));
+    Dart_ListLength(handle, &length);
+
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
+    v8::Local<v8::Array> indexes = v8::Array::New(v8Isolate, length);
+    for (int i = 0; i < length; i++)
+        indexes->Set(i, v8::Integer::New(v8Isolate, i));
+
+    v8SetReturnValue(info, indexes);
+}
+
+v8::Handle<v8::Array> shallowListToV8(Dart_Handle value, DartDOMData* domData, Dart_Handle& exception)
+{
+    ASSERT(Dart_IsList(value));
+
+    intptr_t length = 0;
+    Dart_Handle result = Dart_ListLength(value, &length);
+    if (!DartUtilities::checkResult(result, exception))
+        return v8::Handle<v8::Array>();
+
+    v8::Local<v8::Array> array = v8::Array::New(v8::Isolate::GetCurrent(), length);
+
+    for (intptr_t i = 0; i < length; ++i) {
+        result = Dart_ListGetAt(value, i);
+        v8::Handle<v8::Value> v8value = JsInterop::fromDart(domData, result, exception);
+        // TODO(jacobr): is there a better way to handle this error case?
+        if (exception)
+            return v8::Handle<v8::Array>();
+        array->Set(i, v8value);
+    }
+    return array;
+}
+
+// If one of the methods we added to the Dart List proxy to make it mascarade
+// as JavaScript Array happens to get called on a JavaScript object instead of
+// a Dart List proxy object we use the corresponding regular JavaScript Array
+// method which will do something plausible in most cases even if the
+// JavaScript object isn't actually a JavaScript array.
+bool handleNonDartProxyThis(const v8::FunctionCallbackInfo<v8::Value>& info, const char* jsMethodName)
+{
+    if (DartHandleProxy::isDartProxy(info.Holder())) {
+        return false;
+    }
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();

[vsm, 2015/06/29 13:49:26]

Do we actually ever get down this path?  And if so, why not throw an exception?

E.g., If I tear off a DOM method and invoke it with a different this, I get a
TypeError.

[Jacob, 2015/06/29 17:56:08]

Yeah it is a bit strange but I'm trying to make this object behave like Array
which keeps on trucking... successfully when called on a non Array object. Added
comment
/// The chrome devtools
// appear to go down exactly this code path as I got crashes in the devtools
// due to info.Holder not being a DartHandleProxy. I haven't investigated
// whether devtools would still function properly if we threw an exception
// which would match the behavior of DOM classes when a method is called on the
// wrong object. The current behavior while strange matches the behavior
// observed when an method from Array is called on an arbitrary JS object.

+    // Get the method on JS array in an inefficient way.
+    v8::Local<v8::Function> method = v8::Array::New(v8Isolate)->Get(v8::String::NewFromUtf8(v8Isolate, jsMethodName)).As<v8::Function>();
+    ASSERT(!method.IsEmpty());
+    int length = info.Length();
+    Vector<v8::Local<v8::Value> > v8Args(length);
+    for (int i = 0; i < length; ++i) {
+        v8Args[i] = info[i];
+    }
+    v8SetReturnValue(info, method->Call(info.Holder(), length, v8Args.data()));
+    return true;
+}
+
+void arrayHelper(const v8::FunctionCallbackInfo<v8::Value>& info, const char* methodName, const char* jsMethodName)
+{
+    if (handleNonDartProxyThis(info, jsMethodName)) {
+        return;
+    }
+    DartScopes scopes(info.Holder());
+    DartDOMData* domData = DartDOMData::current();
+    Dart_Handle handle = scopes.handle;
+    Dart_Handle ret = Dart_Invoke(domData->jsLibrary(), Dart_NewStringFromCString(methodName), 1, &handle);
+    setJsReturnValue(domData, info, ret);
+}
+
+void arrayHelper1Arg(const v8::FunctionCallbackInfo<v8::Value>& info, const char* methodName, const char* jsMethodName)
+{
+    if (handleNonDartProxyThis(info, jsMethodName)) {
+        return;
+    }
+    DartScopes scopes(info.Holder());
+    DartDOMData* domData = DartDOMData::current();
+    Dart_Handle handle = scopes.handle;
+    Dart_Handle e;
+    if (info.Length() == 0) {
+        e = Dart_Null();
+    } else {
+        e = JsInterop::toDart(info[0]);
+    }
+    Dart_Handle args[2] = { handle, e };
+    Dart_Handle ret = Dart_Invoke(domData->jsLibrary(), Dart_NewStringFromCString(methodName), 2, args);
+    setJsReturnValue(domData, info, ret);
+}
+
+void arrayHelperWithArgsAsList(const v8::FunctionCallbackInfo<v8::Value>& info, const char* methodName, const char* jsMethodName)
+{
+    if (handleNonDartProxyThis(info, jsMethodName)) {
+        return;
+    }
+    DartScopes scopes(info.Holder());
+    DartDOMData* domData = DartDOMData::current();
+    Dart_Handle handle = scopes.handle;
+    int length = info.Length();
+    Dart_Handle argsList = Dart_NewList(length);
+    for (int i = 0; i < length; ++i) {
+        Dart_ListSetAt(argsList, i, JsInterop::toDart(info[i]));
+    }
+    // Note: this is also just info.Holder().
+    Dart_Handle args[2] = { handle, argsList };
+    setJsReturnValue(domData, info, Dart_Invoke(domData->jsLibrary(), Dart_NewStringFromCString(methodName), 2, args));
+}
+
+static void arrayNamedPropertyGetter(v8::Local<v8::String> name, const v8::PropertyCallbackInfo<v8::Value>& info)
+{
+    if (!DartHandleProxy::isDartProxy(info.Holder())) {
+        // I don't think this case can occur but avoid crashing if there is an
+        // exotic way to trigger it.
+        return;
+    }
+
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
+    if (!name->Equals(v8::String::NewFromUtf8(v8Isolate, "length")))
+        return;
+
+    DartScopes scopes(info.Holder());
+    Dart_Handle handle = scopes.handle;
+
+    intptr_t length = 0;
+    Dart_ListLength(handle, &length);
+    v8SetReturnValueInt(info, length);
+}
+
+static void arrayNamedPropertySetter(v8::Local<v8::String> property, v8::Local<v8::Value> value, const v8::PropertyCallbackInfo<v8::Value>& info)
+{
+    if (!DartHandleProxy::isDartProxy(info.Holder())) {
+        // I don't think this case can occur but avoid crashing if there is an
+        // exotic way to trigger it.
+        return;
+    }
+
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
+    if (!property->Equals(v8::String::NewFromUtf8(v8Isolate, "length"))) {
+        return;
+    }
+
+    DartScopes scopes(info.Holder());
+    Dart_Handle handle = scopes.handle;
+    DartDOMData* domData = DartDOMData::current();
+    Dart_Handle args[2] = { handle, JsInterop::toDart(value) };
+    Dart_Handle ret = Dart_Invoke(domData->jsLibrary(), Dart_NewStringFromCString("_setListLength"), 2, args);
+    setJsReturnValue(domData, info, ret);
+}
+
+static void arrayQueryProperty(v8::Local<v8::String> name, const v8::PropertyCallbackInfo<v8::Integer>& info)
+{
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
+    if (name->Equals(v8::String::NewFromUtf8(v8Isolate, "length"))) {
+        v8SetReturnValueInt(info, v8::DontEnum | v8::DontDelete);
+    }
+}
+
+static void arrayDeleteProperty(v8::Local<v8::String> name, const v8::PropertyCallbackInfo<v8::Boolean>& info)
+{
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
+    if (name->Equals(v8::String::NewFromUtf8(v8Isolate, "length"))) {
+        v8SetReturnValueBool(info, false);
+    }
+}
+
+void arrayToStringCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelper(info, "_arrayToString", "toString");
+}
+
+
+void arrayJoinCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelper1Arg(info, "_arrayJoin", "join");
+}
+
+void arrayPushCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelperWithArgsAsList(info, "_arrayPush", "push");
+}
+
+void arrayPopCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelper(info, "_arrayPop", "pop");
+}
+
+void concatCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelperWithArgsAsList(info, "_arrayConcat", "concat");
+}
+
+void arrayReverseCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelper(info, "_arrayReverse", "reverse");
+}
+
+void arrayShiftCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelper(info, "_arrayShift", "shift");
+}
+
+void arrayUnshiftCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelperWithArgsAsList(info, "_arrayUnshift", "unshift");
+}
+
+void arraySpliceCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    arrayHelperWithArgsAsList(info, "_arraySplice", "splice");
+}
+
+void toJsArrayCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    // This isn't a method on the JavaScript Array class so it is fine to
+    // just return the existing hopefully Array like JS object if not called on
+    // a Dart List.
+    if (!DartHandleProxy::isDartProxy(info.Holder())) {
+        v8SetReturnValue(info, info.Holder());
+    }
+    DartScopes scopes(info.Holder());
+    DartDOMData* domData = DartDOMData::current();
+    Dart_Handle handle = scopes.handle;
+    Dart_Handle exception = 0;
+    v8::Local<v8::Array> v8Array = shallowListToV8(handle, domData, exception);
+    ASSERT(!exception);
+    v8SetReturnValue(info, v8Array);
+}
+
+void arraySortCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    // TODO(jacobr): consider using the JavaScript sort method instead.
+    arrayHelper1Arg(info, "_arraySort", "sort");
+}
+
+v8::Local<v8::FunctionTemplate> dartListTemplate()
+{
+    DEFINE_STATIC_LOCAL(v8::Persistent<v8::FunctionTemplate>, proxyTemplate, ());
+    v8::Local<v8::FunctionTemplate> proxyTemplateLocal;
+    v8::Isolate* v8Isolate = v8::Isolate::GetCurrent();
+    if (proxyTemplate.IsEmpty()) {
+        proxyTemplate.Reset(v8::Isolate::GetCurrent(), v8::FunctionTemplate::New(v8Isolate));
+        proxyTemplateLocal = v8::Local<v8::FunctionTemplate>::New(v8Isolate, proxyTemplate);
+        // Set to Array because we want these instances to appear to be
+        // JavaScript arrays as far as user code is concerned.
+        proxyTemplateLocal->SetClassName(v8::String::NewFromUtf8(v8Isolate, "Array"));
+        // Hack to set the prototype to be the prototype of an actual JavaScript Array.
+
+        v8::Local<v8::ObjectTemplate> protoTemplate  = proxyTemplateLocal->PrototypeTemplate();
+
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "toString"), v8::FunctionTemplate::New(v8Isolate, arrayToStringCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "join"), v8::FunctionTemplate::New(v8Isolate, arrayJoinCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "push"), v8::FunctionTemplate::New(v8Isolate, arrayPushCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "pop"), v8::FunctionTemplate::New(v8Isolate, arrayPopCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "concat"), v8::FunctionTemplate::New(v8Isolate, concatCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "reverse"), v8::FunctionTemplate::New(v8Isolate, arrayReverseCallback), v8::DontEnum);
+
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "shift"), v8::FunctionTemplate::New(v8Isolate, arrayShiftCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "unshift"), v8::FunctionTemplate::New(v8Isolate, arrayUnshiftCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "splice"), v8::FunctionTemplate::New(v8Isolate, arraySpliceCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "sort"), v8::FunctionTemplate::New(v8Isolate, arraySortCallback), v8::DontEnum);
+        protoTemplate ->Set(v8::String::NewFromUtf8(v8Isolate, "$toJsArray"), v8::FunctionTemplate::New(v8Isolate, toJsArrayCallback), v8::DontEnum);
+
+        // ES6 experimental properties not currently supported that we could support if needed.
+        // These would require building separate live proxy objects.
+        // "entries",
+        // "values",
+        // "keys"
+
+        v8::Local<v8::ObjectTemplate> instanceTemplate = setupInstanceTemplate(proxyTemplateLocal);
+        instanceTemplate->SetIndexedPropertyHandler(&indexedGetterArray, &indexedSetterArray, 0, 0, &indexedEnumeratorArray);
+        instanceTemplate->SetNamedPropertyHandler(&arrayNamedPropertyGetter, &arrayNamedPropertySetter, &arrayQueryProperty, &arrayDeleteProperty, 0);
+    } else {
+        proxyTemplateLocal = v8::Local<v8::FunctionTemplate>::New(v8Isolate, proxyTemplate);
+    }
+    return proxyTemplateLocal;
+}
+
 }