[PR] Add a number of CSSOM interfaces + fix HTMLStyleElement.sheet type

Summary:
Fixes #2943 and #2696
- CSSStyleSheet - https://www.w3.org/TR/cssom-1/#the-cssstylesheet-interface
- CSSStyleRule - https://www.w3.org/TR/cssom-1/#cssstylerule
- CSSMediaRule - https://www.w3.org/TR/cssom-1/#the-cssmediarule-interface
- CSSConditionRule - https://developer.mozilla.org/en-US/docs/Web/API/CSSConditionRule
- CSSGroupingRule - https://www.w3.org/TR/2016/WD-cssom-1-20160317/#the-cssgroupingrule-interface
Pull Request resolved: #8071

Reviewed By: nmote

Differential Revision: D17329043

Pulled By: mvitousek

fbshipit-source-id: de76eba9201d797a44261ccb81897cf5d45cde32

Author: kof

lib/cssom.js

@@ -7,12 +7,12 @@
 
 declare class StyleSheet {
   disabled: boolean;
-  href: string;
-  media: MediaList;
-  ownerNode: Node;
-  parentStyleSheet: ?StyleSheet;
-  title: string;
-  type: string;
+  +href: string;
+  +media: MediaList;
+  +ownerNode: Node;
+  +parentStyleSheet: ?StyleSheet;
+  +title: string;
+  +type: string;
 }
 
 declare class StyleSheetList {
@@ -32,17 +32,36 @@ declare class MediaList {
 }
 
 declare class CSSStyleSheet extends StyleSheet {
-  cssRules: CSSRuleList;
-  ownerRule: ?CSSRule;
+  +cssRules: CSSRuleList;
+  +ownerRule: ?CSSRule;
+  deleteRule(index: number): void;
+  insertRule(rule: string, index: number): number;
+}
+
+declare class CSSGroupingRule extends CSSRule {
+  +cssRules: CSSRuleList;
   deleteRule(index: number): void;
-  insertRule(rule: string, index: number): void;
+  insertRule(rule: string, index: number): number;
+}
+
+declare class CSSConditionRule extends CSSGroupingRule {
+  conditionText: string;
+}
+
+declare class CSSMediaRule extends CSSConditionRule {
+  +media: MediaList;
+}
+
+declare class CSSStyleRule extends CSSRule {
+  selectorText: string;
+  +style: CSSStyleDeclaration;
 }
 
 declare class CSSRule {
   cssText: string;
-  parentRule: ?CSSRule;
-  parentStyleSheet: ?CSSStyleSheet;
-  type: number;
+  +parentRule: ?CSSRule;
+  +parentStyleSheet: ?CSSStyleSheet;
+  +type: number;
   static STYLE_RULE: number;
   static MEDIA_RULE: number;
   static FONT_FACE_RULE: number;

lib/dom.js

@@ -3511,7 +3511,7 @@ declare class HTMLStyleElement extends HTMLElement {
   disabled: boolean;
   media: string;
   scoped: boolean;
-  sheet: ?StyleSheet;
+  sheet: ?CSSStyleSheet;
   type: string;
 }