Specs: define how importing element registrations works, move built-in elements to a separate modul…

sky/specs/elements.md

 Sky DOM APIs
 ============
 
 ```dart
-SKY MODULE
-<!-- part of dart:sky -->
-
-<script>
 // ELEMENT TREE API
 
 abstract class Node extends EventTarget {
   @override
   external List<EventTarget> getEventDispatchChain(); // O(N) in number of ancestors across shadow trees
   // implements EventTarget.getEventDispatchChain()
   // returns the event dispatch chain (including handling shadow trees)
 
   external Root get owner; // O(1)
 
@@ skipping 252 matching lines @@
 
 class ApplicationRoot extends Root {
   ApplicationRoot ({List children}) : super(children: children); // O(N) in number of children nodes arguments plus all their descendants
 
   @override
   Type getLayoutManager() => rootLayoutManager; // O(1)
 }
 
 Type rootLayoutManager = BlockLayoutManager; // O(1)
 
-
-// BUILT-IN ELEMENTS
-
-@tagname('import')
-class ImportElement extends Element {
-  ImportElement = Element;
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('template')
-class TemplateElement extends Element {
-  TemplateElement = Element;
-
-  // TODO(ianh): convert <template> to using a token stream instead of a Fragment
-
-  external Fragment get content; // O(1)
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('script')
-class ScriptElement extends Element {
-  ScriptElement = Element;
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('style')
-class StyleElement extends Element {
-  StyleElement = Element;
-
-  external List<Rule> getRules(); // O(N) in rules
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('content')
-class ContentElement extends Element {
-  ContentElement = Element;
-
-  external List<Node> getDistributedNodes(); // O(N) in distributed nodes
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('img')
-class ImgElement extends Element {
-  ImgElement = Element;
-
-  @override
-  Type getLayoutManager() => ImgElementLayoutManager; // O(1)
-}
-
-@tagname('div')
-class DivElement extends Element {
-  DivElement = Element;
-}
-
-@tagname('span')
-class SpanElement extends Element {
-  SpanElement = Element;
-}
-
-@tagname('iframe')
-class IframeElement extends Element {
-  IframeElement = Element;
-
-  @override
-  Type getLayoutManager() => IframeElementLayoutManager; // O(1)
-}
-
-@tagname('t')
-class TElement extends Element {
-  TElement = Element;
-}
-
-@tagname('a')
-class AElement extends Element {
-  AElement = Element;
-}
-
-@tagname('title')
-class TitleElement extends Element {
-  TitleElement = Element;
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-class _ErrorElement extends Element {
-  _ErrorElement._create();
-
-  @override
-  Type getLayoutManager() => _ErrorElementLayoutManager; // O(1)
-}
-
 class SelectorQuery {
   external SelectorQuery(String selector); // O(F()) where F() is the complexity of the selector
 
   external bool matches(Element element); // O(F())
   external Element find(Node root); // O(N*F())+O(M) where N is the number of descendants and M the average depth of the tree
   external List<Element> findAll(Node root); // O(N*F())+O(N*M) where N is the number of descendants and M the average depth of the tree
   // find() and findAll() throw if the root is not one of the following:
   //  - Element
   //  - Fragment
   //  - Root
 }
-</script>
 ```