Expose the CSSSupportsRule interface object

LayoutTests/css3/supports-cssom-expected.txt

 Test CSSSupportRule.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
 PASS CSSRule.SUPPORTS_RULE is defined.
 rules = document.styleSheets[1].cssRules
 PASS rules.length is 4
+PASS rules[0] is an instance of CSSSupportsRule
 PASS rules[0].type is CSSRule.SUPPORTS_RULE
 PASS rules[0].cssRules.length is 2
 PASS rules[0].cssRules[0].type is CSSRule.STYLE_RULE
+PASS rules[0].cssRules[1] is an instance of CSSSupportsRule
 PASS rules[0].cssRules[1].type is CSSRule.SUPPORTS_RULE
 PASS rules[0].cssRules[1].cssRules.length is 1
 PASS rules[0].cssRules[1].cssRules[0].type is CSSRule.STYLE_RULE
 PASS rules[0].conditionText is "(width: 0)"
 PASS rules[0].cssText is "@supports (width: 0) {\n  s { width: 0px; }\n  @supports (width: 1) {\n  s { color: rgb(0, 0, 0); }\n}\n}"
 
 Inserting and deleting rules.
 rules[0].insertRule('@media all { #s { width: 0px; } }', 2)
 PASS rules[0].cssRules.length is 3
 PASS rules[0].cssRules[2].type is CSSRule.MEDIA_RULE
 rules[0].deleteRule(2)
 PASS rules[0].cssRules.length is 2
 rules[0].cssRules[1].insertRule('@supports (display: rainbow) {}', 1)
 PASS rules[0].cssRules[1].cssRules.length is 2
+PASS rules[0].cssRules[1].cssRules[1] is an instance of CSSSupportsRule
 PASS rules[0].cssRules[1].cssRules[1].type is CSSRule.SUPPORTS_RULE
 rules[0].cssRules[1].deleteRule(1)
 PASS rules[0].cssRules.length is 2
 
 @charset, @namespace, @import rules are not allowed inside @supports.
 PASS rules[0].insertRule('@charset "UTF-8"', 2) threw exception SyntaxError: Failed to execute 'insertRule' on 'CSSSupportsRule': the rule '@charset "UTF-8"' is invalid and cannot be parsed..
 PASS rules[0].insertRule('@namespace ""', 2) threw exception SyntaxError: Failed to execute 'insertRule' on 'CSSSupportsRule': the rule '@namespace ""' is invalid and cannot be parsed..
 PASS rules[0].insertRule('@import url("../fast/cssom/resources/import.css")', 2) threw exception HierarchyRequestError: Failed to execute 'insertRule' on 'CSSSupportsRule': '@import' rules cannot be inserted inside a group rule..
 
 Whitespace and formatting should be preserved within the condition, whitespace outside the condition should be trimmed.
 PASS rules[1].conditionText is "((  (     padding: 0)    and (display: none)) or (display: rainbow))"
 
 @supports rule nested inside a media rule.
 PASS rules[2].type is CSSRule.MEDIA_RULE
 PASS rules[2].cssRules.length is 1
+PASS rules[2].cssRules[0] is an instance of CSSSupportsRule
 PASS rules[2].cssRules[0].type is CSSRule.SUPPORTS_RULE
 PASS rules[2].cssRules[0].conditionText is "( padding: 0)"
 PASS rules[0].cssRules[1].cssRules.length is 1
 PASS rules[2].cssRules[0].cssRules[0].type is CSSRule.PAGE_RULE
 PASS rules[2].cssText is "@media all { \n  @supports ( padding: 0) {\n  @page :left { top: 0px; }\n}\n}"
 
 No extra parens should be added to the conditionText.
 PASS rules[3].conditionText is "(border: black) and (padding: 0) and (width: 0)"
 
 Deleting a top-level rule should work correctly.
 document.styleSheets[1].deleteRule(3)
 PASS rules.length is 3
 PASS rules[0].type is CSSRule.SUPPORTS_RULE
 PASS rules[0].cssRules.length is 2
 PASS rules[0].cssRules[0].type is CSSRule.STYLE_RULE
 PASS rules[0].cssRules[1].type is CSSRule.SUPPORTS_RULE
 PASS rules[0].cssRules[1].cssRules.length is 1
 PASS rules[0].cssRules[1].cssRules[0].type is CSSRule.STYLE_RULE
 PASS successfullyParsed is true
 
 TEST COMPLETE