Make it possible for sky-element to register any tag name

... instead of hard-coding "example".

We do this by adding a custom constructor for Element that gets the |tagName|
property off the instance.

R=esprehn@chromium.org

Review URL: https://codereview.chromium.org/943153002

engine/bindings/BUILD.gn

@@ -13,6 +13,7 @@ source_set("bindings") {
     "builtin_natives.h",
     "builtin_sky.cc",
     "builtin_sky.h",
+    "custom/dart_element_custom.cc",
     "dart_callback.cc",
     "dart_callback.h",
     "dart_event_listener.cc",

engine/bindings/custom/dart_element_custom.cc

+// Copyright 2015 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 "sky/engine/config.h"
+#include "sky/engine/core/dom/Element.h"
+
+#include "dart/runtime/include/dart_api.h"
+#include "sky/engine/core/script/dom_dart_state.h"
+#include "sky/engine/tonic/dart_converter.h"
+
+namespace blink {
+namespace DartElementInternal {
+
+void constructorCallback(Dart_NativeArguments args) {
+  Dart_Handle receiver = Dart_GetNativeArgument(args, 0);
+  DCHECK(!LogIfError(receiver));
+
+  Dart_Handle tag_name = Dart_GetField(receiver,
+                                       Dart_NewStringFromCString("tagName"));
+  if (!Dart_IsString(tag_name)) {
+    Dart_ThrowException(Dart_NewStringFromCString("tagName is not a string"));
+    return;
+  }
+
+  RefPtr<Element> element = Element::create(
+      QualifiedName(StringFromDart(tag_name)), DOMDartState::CurrentDocument());
+
+  // TODO(abarth): We should remove these states because elements are never
+  // waiting for upgrades.
+  element->setCustomElementState(Element::WaitingForUpgrade);
+  element->setCustomElementState(Element::Upgraded);
+  element->AssociateWithDartWrapper(args);
+}
+
+}  // namespace DartElementInternal
+}  // namespace blink

engine/bindings/scripts/templates/interface_dart.template

@@ -19,11 +19,11 @@ part of sky.core;
     {%- endfor -%}
 {%- endmacro -%}
 
-{% if not constructors %}abstract {% endif -%}
+{% if not constructors and not custom_constructors %}abstract {% endif -%}
 class {{interface_name}} extends {{ parent_interface if parent_interface else 'NativeFieldWrapperClass2' }} {
     // Constructors
 {# TODO(eseidel): We only ever have one constructor. #}
-{%- for constructor in constructors %}
+{%- for constructor in constructors + custom_constructors %}
     void _constructor(
     {%- for arg in constructor.arguments -%}
         {{ arg.dart_type }} {{ arg.name }}{% if not loop.last %}, {% endif %}

engine/core/dom/Element.cpp

@@ -87,17 +87,6 @@
 
 namespace blink {
 
-PassRefPtr<Element> Element::create(Document& document, const AtomicString& tagName)
-{
-    DCHECK(DartState::Current()) << "This function should be used only by the bindings";
-    RefPtr<Element> element = create(QualifiedName(tagName), &document);
-    // TODO(abarth): We should remove these states because elements are never
-    // waiting for upgrades.
-    element->setCustomElementState(Element::WaitingForUpgrade);
-    element->setCustomElementState(Element::Upgraded);
-    return element.release();
-}
-
 PassRefPtr<Element> Element::create(const QualifiedName& tagName, Document* document)
 {
     return adoptRef(new Element(tagName, document, CreateElement));

engine/core/dom/Element.h

@@ -65,9 +65,6 @@ enum SpellcheckAttributeState {
 class Element : public ContainerNode {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    // Used for custom elements.
-    static PassRefPtr<Element> create(Document& document, const AtomicString& tagName);
-
     static PassRefPtr<Element> create(const QualifiedName&, Document*);
     virtual ~Element();
 

engine/core/dom/Element.idl

@@ -3,8 +3,7 @@
 // found in the LICENSE file.
 
 [
-  Constructor(DOMString tagName),
-  ConstructorCallWith=Document,
+  CustomConstructor,
 ] interface Element : ParentNode {
   readonly attribute DOMString tagName;
 

framework/sky-element.sky

@@ -34,9 +34,7 @@ abstract class SkyElement extends Element {
 
   String get tagName => _getTagName(runtimeType);
 
-  // TODO(abarth): Rather than hard-coding "example" here, we should make the
-  // bindings read the |tagName| property of this object during construction.
-  SkyElement() : super("example") {
+  SkyElement() {
     created();
 
     // Invoke attributeChanged callback when element is first created too.