Updating dwc for breaking changes that will be part of the next sdk

lib/web_components.dart

Index: lib/web_components.dart
diff --git a/lib/web_components.dart b/lib/web_components.dart
index 7984dddfcec10e6685345887bcab7f951ebd4037..21bfa57b7bb7ffebec46b2d7e22f20a4e0a1983a 100644
--- a/lib/web_components.dart
+++ b/lib/web_components.dart
@@ -331,9 +331,9 @@ abstract class WebComponent implements Element {
   Map<String, String> getNamespacedAttributes(String namespace) =>
       _element.getNamespacedAttributes(namespace);
 
-  Future<CSSStyleDeclaration> get computedStyle => _element.computedStyle;
+  Future<CssStyleDeclaration> get computedStyle => _element.computedStyle;
 
-  Future<CSSStyleDeclaration> getComputedStyle(String pseudoElement)
+  Future<CssStyleDeclaration> getComputedStyle(String pseudoElement)
     => _element.getComputedStyle(pseudoElement);
 
   Element clone(bool deep) => _element.clone(deep);
@@ -402,7 +402,7 @@ abstract class WebComponent implements Element {
 
   Element get previousElementSibling => _element.previousElementSibling;
 
-  CSSStyleDeclaration get style => _element.style;
+  CssStyleDeclaration get style => _element.style;
 
   String get tagName => _element.tagName;
 
@@ -440,7 +440,7 @@ abstract class WebComponent implements Element {
 
   List<Element> queryAll(String selectors) => _element.queryAll(selectors);
 
-  HTMLCollection get $dom_children => _element.$dom_children;
+  HtmlCollection get $dom_children => _element.$dom_children;
 
   int get $dom_childElementCount => _element.$dom_childElementCount;
 
@@ -455,12 +455,6 @@ abstract class WebComponent implements Element {
 
   int get clientWidth => _element.clientWidth;
 
-  int get childElementCount => _element.childElementCount;
-
-  Element get firstElementChild => _element.firstElementChild;
-
-  Element get lastElementChild => _element.lastElementChild;
-
   Element get $dom_firstElementChild => _element.$dom_firstElementChild;
 
   Element get $dom_lastElementChild => _element.$dom_lastElementChild;