[cssom] Per WG resolution, tombstone the CSSRule.type attribute. Fixes w3c#4142.

Author: tabatkins

cssom-1/Overview.bs

@@ -1706,45 +1706,23 @@ inherits from this interface.
 <pre class=idl>
 [Exposed=Window]
 interface CSSRule {
+  attribute CSSOMString cssText;
+  readonly attribute CSSRule? parentRule;
+  readonly attribute CSSStyleSheet? parentStyleSheet;
+
+  // the following attribute and constants are historial
+  readonly attribute unsigned short type;
   const unsigned short STYLE_RULE = 1;
-  const unsigned short CHARSET_RULE = 2; // historical
+  const unsigned short CHARSET_RULE = 2;
   const unsigned short IMPORT_RULE = 3;
   const unsigned short MEDIA_RULE = 4;
   const unsigned short FONT_FACE_RULE = 5;
   const unsigned short PAGE_RULE = 6;
   const unsigned short MARGIN_RULE = 9;
   const unsigned short NAMESPACE_RULE = 10;
-  readonly attribute unsigned short type;
-  attribute CSSOMString cssText;
-  readonly attribute CSSRule? parentRule;
-  readonly attribute CSSStyleSheet? parentStyleSheet;
 };
 </pre>
 
-The <dfn attribute for=CSSRule>type</dfn> attribute must return the CSS rule type, as follows:
-
-<dl class=switch>
- <dt>If the object is a {{CSSStyleRule}}
- <dd>Return <dfn const for=CSSRule>STYLE_RULE</dfn> (numeric value 1).
- <dt>If the object is a {{CSSImportRule}}
- <dd>Return <dfn const for=CSSRule>IMPORT_RULE</dfn> (numeric value 3).
- <dt>If the object is a {{CSSMediaRule}}
- <dd>Return <dfn const for=CSSRule>MEDIA_RULE</dfn> (numeric value 4).
- <dt>If the object is a {{CSSFontFaceRule}}
- <dd>Return <dfn const for=CSSRule>FONT_FACE_RULE</dfn> (numeric value 5).
- <dt>If the object is a {{CSSPageRule}}
- <dd>Return <dfn const for=CSSRule>PAGE_RULE</dfn> (numeric value 6).
- <dt>If the object is a {{CSSMarginRule}}
- <dd>Return <dfn const for=CSSRule>MARGIN_RULE</dfn> (numeric value 9).
- <dt>If the object is a {{CSSNamespaceRule}}
- <dd>Return <dfn const for=CSSRule>NAMESPACE_RULE</dfn> (numeric value 10).
- <dt>Otherwise
- <dd>Return a value defined on the <a href="https://wiki.csswg.org/spec/cssom-constants">CSSOM Constants</a> wiki page.
-</dl>
-
-Note: The value 0, formerly known as <code>UNKNOWN_RULE</code>, is made
-obsolete by this specification. This value will not be re-allocated in the future and will remain reserved.
-
 The <dfn attribute for=CSSRule>cssText</dfn> attribute must return a <a lt="serialize a CSS rule">serialization</a> of the
 <a for=/>CSS rule</a>.
 On setting the {{CSSRule/cssText}} attribute must do nothing.
@@ -1764,6 +1742,47 @@ Note: Removing a <code>Node</code> that implements the <code>LinkStyle</code> in
 {{Document}} instance does not (by itself) cause the <code>CSSStyleSheet</code> referenced by a <code>CSSRule</code> to be
 unreachable.
 
+The <dfn attribute for=CSSRule>type</dfn> attribute is deprecated.
+It must return an integer, as follows:
+
+<dl class=switch dfn-type=const dfn-for=CSSRule>
+ <dt>If the object is a {{CSSStyleRule}}
+ <dd>Return 1.
+ <dt>If the object is a {{CSSImportRule}}
+ <dd>Return 3.
+ <dt>If the object is a {{CSSMediaRule}}
+ <dd>Return 4.
+ <dt>If the object is a {{CSSFontFaceRule}}
+ <dd>Return 5.
+ <dt>If the object is a {{CSSPageRule}}
+ <dd>Return 6.
+ <dt>If the object is a {{CSSKeyframesRule}}
+ <dd>Return 7.
+ <dt>If the object is a {{CSSKeyframeRule}}
+ <dd>Return 8.
+ <dt>If the object is a {{CSSMarginRule}}
+ <dd>Return 9.
+ <dt>If the object is a {{CSSNamespaceRule}}
+ <dd>Return 10.
+ <dt>If the object is a {{CSSCounterStyleRule}}
+ <dd>Return 11.
+ <dt>If the object is a {{CSSSupportsRule}}
+ <dd>Return 12.
+ <dt>If the object is a {{CSSFontFeatureValuesRule}}
+ <dd>Return 14.
+ <dt>If the object is a {{CSSViewportRule}}
+ <dd>Return 15.
+ <dt>Otherwise
+ <dd>Return 0.
+</dl>
+
+Note: The practice of using an integer enumeration
+and several constants to <em>identify</em> the integers
+is a legacy design practice that is no longer used in Web APIs.
+Instead, to tell what type of rule a given object is,
+it is recommended to check <code highlight=js>rule.constructor.name</code>,
+which will return a string like <code highlight=js>"CSSStyleRule"</code>.
+
 
 ### The {{CSSStyleRule}} Interface ### {#the-cssstylerule-interface}