Make a few DOM properties nullable and IDL classes iterable

Summary:
These DOM properties are definitely nullable, though in the average case they probably exist. I assume it's best for the type definitions to cover all the possibilities.

For the iterability, Chome added these in a few releases ago and the next release of core-js should include polyfill logic for them. More info in zloirock/core-js#249
Closes #3127

Differential Revision: D4388268

Pulled By: gabelevi

fbshipit-source-id: 282238b38f82fb71db87f88eb7f9583c20286724

lib/cssom.js

@@ -19,11 +19,13 @@ declare class StyleSheet {
 }
 
 declare class StyleSheetList {
+  @@iterator(): Iterator<StyleSheet>;
   length: number;
   [index: number]: StyleSheet;
 }
 
 declare class MediaList {
+  @@iterator(): Iterator<string>;
   mediaText: string;
   length: number;
   item(index: number): ?string;
@@ -63,11 +65,14 @@ declare class CSSRule {
 }
 
 declare class CSSRuleList {
+  @@iterator(): Iterator<CSSRule>;
   length: number;
   item(index: number): ?CSSRule;
+  [index: number]: CSSRule;
 }
 
 declare class CSSStyleDeclaration {
+  @@iterator(): Iterator<string>;
   /* DOM CSS Properties */
   alignContent: string;
   alignItems: string;
@@ -368,6 +373,7 @@ declare class CSSStyleDeclaration {
   getPropertyPriority(property: string): string;
   getPropertyValue(property:string): string;
   item(index: number): string;
+  [index: number]: string;
   length: number;
   parentRule: CSSRule;
   removeProperty(property: string): string;

lib/dom.js

@@ -67,6 +67,7 @@ declare class DataTransfer {
 }
 
 declare class DataTransferItemList {
+  @@iterator(): Iterator<DataTransferItem>;
   length: number; // readonly
   [index: number]: DataTransferItem;
   add(data: string, type: string): ?DataTransferItem;
@@ -347,6 +348,7 @@ declare class Touch {
 // TouchList#item(index) will return null if n > #length. Should #item's
 // return type just been Touch?
 declare class TouchList {
+  @@iterator(): Iterator<Touch>;
   length: number,
   item(index: number): null | Touch,
   [index: number]: Touch,
@@ -423,9 +425,15 @@ declare class NodeList<T> {
   length: number;
   item(index: number): T;
   [index: number]: T;
+
+  forEach(callbackfn: (value: T, index: number, list: NodeList<T>) => any, thisArg?: any): void;
+  entries(): Iterator<[number, T]>;
+  keys(): Iterator<number>;
+  values(): Iterator<T>;
 }
 
 declare class NamedNodeMap {
+  @@iterator(): Iterator<Attr>;
   length: number;
   removeNamedItemNS(namespaceURI: string, localName: string): Attr;
   item(index: number): Attr;
@@ -440,7 +448,7 @@ declare class NamedNodeMap {
 declare class Attr extends Node {
   isId: boolean;
   specified: boolean;
-  ownerElement: Element;
+  ownerElement: Element | null;
   value: string;
   name: string;
   namespaceURI: string | null;
@@ -494,7 +502,7 @@ declare class Document extends Node {
   adoptNode<T: Node>(source: T): T;
   anchors: HTMLCollection<HTMLAnchorElement>;
   applets: HTMLCollection<HTMLAppletElement>;
-  body: HTMLElement;
+  body: HTMLElement | null;
   characterSet: string;
   close(): void;
   cookie: string;
@@ -534,14 +542,14 @@ declare class Document extends Node {
   createElementNS(namespaceURI: string | null, qualifiedName: string): Element;
   createTextNode(data: string): Text;
   currentScript: HTMLScriptElement | null;
-  doctype: DocumentType;
-  documentElement: HTMLElement;
+  doctype: DocumentType | null;
+  documentElement: HTMLElement | null;
   documentMode: number;
   domain: string | null;
   embeds: HTMLCollection<HTMLEmbedElement>;
   execCommand(cmdID: string, showUI?: boolean, value?: any): boolean;
   forms: HTMLCollection<HTMLFormElement>;
-  getElementById(elementId: string): HTMLElement;
+  getElementById(elementId: string): HTMLElement | null;
   getElementsByClassName(classNames: string): HTMLCollection<HTMLElement>;
   getElementsByName(elementName: string): HTMLCollection<HTMLElement>;
   getElementsByTagName(name: 'a'): HTMLCollection<HTMLAnchorElement>;
@@ -600,7 +608,7 @@ declare class Document extends Node {
   getElementsByTagNameNS(namespaceURI: string | null, localName: 'tr'): HTMLCollection<HTMLTableRowElement>;
   getElementsByTagNameNS(namespaceURI: string | null, localName: 'td' | 'th'): HTMLCollection<HTMLTableCellElement>;
   getElementsByTagNameNS(namespaceURI: string | null, localName: string): HTMLCollection<HTMLElement>;
-  head: HTMLElement;
+  head: HTMLElement | null;
   images: HTMLCollection<HTMLImageElement>;
   implementation: DOMImplementation;
   importNode<T: Node>(importedNode: T, deep: boolean): T;
@@ -625,7 +633,7 @@ declare class Document extends Node {
   getSelection(): Selection | null;
 
   // 6.4.6 Focus management APIs
-  activeElement: HTMLElement;
+  activeElement: HTMLElement | null;
   hasFocus(): boolean;
 
   // extension
@@ -840,12 +848,18 @@ declare var document: Document;
 // TODO: HTMLDocument
 
 declare class DOMTokenList {
+  @@iterator(): Iterator<string>;
   length: number;
   item(index: number): string;
   contains(token: string): boolean;
   add(token: string): void;
   remove(token: string): void;
   toggle(token: string): boolean;
+
+  forEach(callbackfn: (value: string, index: number, list: DOMTokenList) => any, thisArg?: any): void;
+  entries(): Iterator<[number, string]>;
+  keys(): Iterator<number>;
+  values(): Iterator<string>;
 }
 
 
@@ -869,7 +883,7 @@ declare class Element extends Node {
   namespaceURI: ?string;
   nextElementSibling: ?Element;
   outerHTML: string;
-  prefix: string;
+  prefix: string | null;
   previousElementSibling: ?Element;
   scrollHeight: number;
   scrollLeft: number;
@@ -881,9 +895,9 @@ declare class Element extends Node {
   dispatchEvent(event: Event): bool;
 
   getAttribute(name?: string): ?string;
-  getAttributeNS(namespaceURI: string | null, localName: string): string;
-  getAttributeNode(name: string): Attr;
-  getAttributeNodeNS(namespaceURI: string | null, localName: string): Attr;
+  getAttributeNS(namespaceURI: string | null, localName: string): string | null;
+  getAttributeNode(name: string): Attr | null;
+  getAttributeNodeNS(namespaceURI: string | null, localName: string): Attr | null;
   getBoundingClientRect(): ClientRect;
   getClientRects(): ClientRect[];
   getElementsByClassName(names: string): HTMLCollection<HTMLElement>;
@@ -961,8 +975,8 @@ declare class Element extends Node {
   scrollIntoView(arg?: (boolean | { behavior?: ('auto' | 'instant' | 'smooth'), block?: ('start' | 'end') })): void;
   setAttribute(name?: string, value?: string): void;
   setAttributeNS(namespaceURI: string | null, qualifiedName: string, value: string): void;
-  setAttributeNode(newAttr: Attr): Attr;
-  setAttributeNodeNS(newAttr: Attr): Attr;
+  setAttributeNode(newAttr: Attr): Attr | null;
+  setAttributeNodeNS(newAttr: Attr): Attr | null;
   setPointerCapture(pointerId: string): void;
   shadowRoot?: ShadowRoot;
   slot?: string;
@@ -2231,6 +2245,7 @@ declare class HTMLCanvasElement extends HTMLElement {
 }
 
 declare class HTMLFormElement extends HTMLElement {
+  @@iterator(): Iterator<HTMLElement>;
   [name: string]: any;
   acceptCharset: string;
   action: string;
@@ -2359,6 +2374,7 @@ declare class TextTrackCue extends EventTarget {
 }
 
 declare class TextTrackCueList {
+  @@iterator(): Iterator<TextTrackCue>;
   length: number;
   [index: number]: TextTrackCue;
   getCueById(id: string): ?TextTrackCue;
@@ -2618,6 +2634,7 @@ declare class HTMLSelectElement extends HTMLElement {
 }
 
 declare class HTMLOptionsCollection {
+  @@iterator(): Iterator<Node>;
   length: number;
   item(index: number): Node;
   namedItem(name: string): Node;
@@ -2862,6 +2879,7 @@ declare class SourceBuffer extends EventTarget {
 }
 
 declare class SourceBufferList extends EventTarget {
+  @@iterator(): Iterator<SourceBuffer>;
   [index: number]: SourceBuffer;
   length: number;
 }