Specs: Drop the concept of late-bound elements. An element can never be upgraded.

sky/specs/apis.md

 APIs
 ====
 
 The Sky core API
 ----------------
 
 ```javascript
 module 'sky:core' {
 
   // EVENTS
@@ skipping 124 matching lines @@
   }
   
   class SelectorQuery {
     constructor (String selector); // O(F()) where F() is the complexity of the selector
 
     Boolean matches(Element element); // O(F())
     Element? find(ParentNode root); // O(N*F()) where N is the number of descendants
     Array<Element> findAll(ParentNode root); // O(N*F()) where N is the number of descendants
   }
 
-  // Built-in Elements
+
+  // BUILT-IN ELEMENTS
+
   class ImportElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "import"
+    constructor attribute Boolean shadow; // O(1) // false
   }
   class TemplateElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "template"
+    constructor attribute Boolean shadow; // O(1) // false
+
     readonly attribute DocumentFragment content; // O(1)
   }
   class ScriptElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "script"
+    constructor attribute Boolean shadow; // O(1) // false
   }
   class StyleElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "style"
+    constructor attribute Boolean shadow; // O(1) // false
   }
   class ContentElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "content"
+    constructor attribute Boolean shadow; // O(1) // false
+
     Array<Node> getDistributedNodes(); // O(N) in distributed nodes
   }
   class ImgElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "img"
+    constructor attribute Boolean shadow; // O(1) // false
+  }
+  class DivElement : Element {
+    constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
+    constructor (ChildArguments... nodes); // shorthand
+    constructor (Dictionary attributes); // shorthand
+    constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "div"
+    constructor attribute Boolean shadow; // O(1) // false
+  }
+  class SpanElement : Element {
+    constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
+    constructor (ChildArguments... nodes); // shorthand
+    constructor (Dictionary attributes); // shorthand
+    constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "span"
+    constructor attribute Boolean shadow; // O(1) // false
   }
   class IframeElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "iframe"
+    constructor attribute Boolean shadow; // O(1) // false
   }
   class TElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "t"
+    constructor attribute Boolean shadow; // O(1) // false
   }
   class AElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "a"
+    constructor attribute Boolean shadow; // O(1) // false
   }
   class TitleElement : Element {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "title"
+    constructor attribute Boolean shadow; // O(1) // false
+  }
+  class ErrorElement : Element {
+    constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
+    constructor (ChildArguments... nodes); // shorthand
+    constructor (Dictionary attributes); // shorthand
+    constructor (); // shorthand
+    constructor attribute String tagName; // O(1) // "error"
+    constructor attribute Boolean shadow; // O(1) // false
   }
 
 
 
+  // MODULES
+
   dictionary ElementRegistration {
     String tagName;
     Boolean shadow = false;
     Object prototype = Element;
   }
 
   interface ElementConstructor {
     constructor (Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
     constructor (ChildArguments... nodes); // shorthand
     constructor (Dictionary attributes); // shorthand
     constructor (); // shorthand
 
     constructor attribute String tagName;
     constructor attribute Boolean shadow;
   }
 
-  // MODULES
   abstract class AbstractModule : EventTarget {
     readonly attribute Document document; // O(1) // the Documentof the module or application
     Promise<any> import(String url); // O(Yikes) // returns the module's exports
 
     readonly attribute String url;
 
-    // createElement() lets you create elements that will be upgraded later when you register the element
-    Element createElement(String tagName, Dictionary attributes, ChildArguments... nodes); // O(M+N), M = number of attributes, N = number of nodes plus all their descendants
-    Element createElement(String tagName, Dictionary attributes); // shorthand
-    Element createElement(String tagName, ChildArguments... nodes); // shorthand
-    Element createElement(String tagName); // shorthand
-
-    ElementConstructor registerElement(ElementRegistration options); // O(N) in number of outstanding elements with that tag name to be upgraded
+    ElementConstructor registerElement(ElementRegistration options); // O(1)
     // if you call registerElement() with an object that was created by
     // registerElement(), it just returns the object after registering it,
     // rather than creating a new constructor
 
     ScriptElement? currentScript; // O(1) // returns the <script> element currently being executed if any, and if it's in this module; else null
   }
 
   class Module : AbstractModule {
     constructor (Application application, Document document, String url); // O(1)
     readonly attribute Application application; // O(1)
@@ skipping 181 matching lines @@
   the core mojo fabric JS API   sky:mojo:fabric:core
   the asyncWait/cancelWait mojo fabric JS API (interface to IPC thread)  sky:mojo:fabric:ipc
   the mojom for the shell, proxying through C++ so that the shell pipe isn't exposed  sky:mojo:shell
   the sky API  sky:core
   the sky debug symbols for private APIs  sky:debug
 ```
 
 TODO(ianh): determine if we want to separate the "this" from the
 Document, especially for Modules, so that exposing a module's element
 doesn't expose the module's exports attribute.