[cssom] Use methods instead of attributes for GetStyleUtils since they always return new objects. https://www.w3.org/Bugs/Public/show_bug.cgi?id=22939

Author: Simon Pieters

cssom/Overview.html

@@ -2810,35 +2810,35 @@ <h3 id="the-getstyleutils-interface"><span class="secno">7.3 </span>The <code ti
 
 <pre class="idl">[NoInterfaceObject]
 interface <dfn id="getstyleutils">GetStyleUtils</dfn> {
-  readonly attribute <a href="#cssstyledeclaration">CSSStyleDeclaration</a> <a href="#dom-getstyleutils-cascadedstyle" title="dom-GetStyleUtils-cascadedStyle">cascadedStyle</a>;
-  <!--readonly attribute <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-defaultStyle>defaultStyle</span>;
-  -->readonly attribute <a href="#cssstyledeclaration">CSSStyleDeclaration</a> <a href="#dom-getstyleutils-rawcomputedstyle" title="dom-GetStyleUtils-rawComputedStyle">rawComputedStyle</a>;
-  readonly attribute <a href="#cssstyledeclaration">CSSStyleDeclaration</a> <a href="#dom-getstyleutils-usedstyle" title="dom-GetStyleUtils-usedStyle">usedStyle</a>;
+  [NewObject] <a href="#cssstyledeclaration">CSSStyleDeclaration</a> <a href="#dom-getstyleutils-cascadedstyle" title="dom-GetStyleUtils-cascadedStyle">cascadedStyle</a>();
+  <!--[NewObject] <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-defaultStyle>defaultStyle</span>();
+  -->[NewObject] <a href="#cssstyledeclaration">CSSStyleDeclaration</a> <a href="#dom-getstyleutils-rawcomputedstyle" title="dom-GetStyleUtils-rawComputedStyle">rawComputedStyle</a>();
+  [NewObject] <a href="#cssstyledeclaration">CSSStyleDeclaration</a> <a href="#dom-getstyleutils-usedstyle" title="dom-GetStyleUtils-usedStyle">usedStyle</a>();
 };</pre>
 
-<p class="atrisk">The <dfn id="dom-getstyleutils-cascadedstyle" title="dom-GetStyleUtils-cascadedStyle"><code>cascadedStyle</code></dfn> attribute must return a new <a href="#css-declaration-block">CSS declaration block</a>
+<p class="atrisk">The <dfn id="dom-getstyleutils-cascadedstyle" title="dom-GetStyleUtils-cascadedStyle"><code>cascadedStyle</code></dfn> attribute must return a <a href="#css-declaration-block">CSS declaration block</a>
 with the <a href="#concept-css-declaration-block-readonly-flag" title="concept-css-declaration-block-readonly-flag">readonly flag</a> set and the
 <a href="#concept-css-declaration-block-declarations" title="concept-css-declaration-block-declarations">declarations</a> set to all longhand properties
 that are <a href="#supported-css-property" title="supported CSS property">supported CSS properties</a> that have a <a href="#cascaded-value">cascaded value</a> for the <a class="external" data-anolis-spec="dom" href="http://dom.spec.whatwg.org/#context-object">context
 object</a>, with the value being the <a href="#cascaded-value">cascaded value</a> computed for the <a class="external" data-anolis-spec="dom" href="http://dom.spec.whatwg.org/#context-object">context object</a> using the style rules
 associated with the <a class="external" data-anolis-spec="dom" href="http://dom.spec.whatwg.org/#context-object">context object</a>'s <a href="#associated-document">associated document</a>.</p>
 
-<!--<p class=atrisk>The <dfn title=dom-GetStyleUtils-defaultStyle><code>defaultStyle</code></dfn> attribute must return a new <span>CSS declaration block</span> with
-the <span title=concept-css-declaration-block-readonly-flag>readonly flag</span> set and the
+<!--<p class=atrisk>The <dfn title=dom-GetStyleUtils-defaultStyle><code>defaultStyle</code></dfn> attribute must return a <span>CSS declaration block</span>
+with the <span title=concept-css-declaration-block-readonly-flag>readonly flag</span> set and the
 <span title=concept-css-declaration-block-declarations>declarations</span> set to all longhand properties that are
 <span title="supported CSS property">supported CSS properties</span> with the value being the
 <span>computed value</span> computed for the <span data-anolis-spec=dom>context object</span> using the user-agent-level style rules and user-level style rules
 associated with the <span data-anolis-spec=dom>context object</span>'s <span>associated document</span>, ignoring transitions, animations, author-level style
 rules, author-level presentational hints and override-level style rules.</p>-->
 
-<p class="atrisk">The <dfn id="dom-getstyleutils-rawcomputedstyle" title="dom-GetStyleUtils-rawComputedStyle"><code>rawComputedStyle</code></dfn> attribute must return a new <a href="#css-declaration-block">CSS declaration
+<p class="atrisk">The <dfn id="dom-getstyleutils-rawcomputedstyle" title="dom-GetStyleUtils-rawComputedStyle"><code>rawComputedStyle</code></dfn> attribute must return a <a href="#css-declaration-block">CSS declaration
 block</a> with the <a href="#concept-css-declaration-block-readonly-flag" title="concept-css-declaration-block-readonly-flag">readonly flag</a> set and the
 <a href="#concept-css-declaration-block-declarations" title="concept-css-declaration-block-declarations">declarations</a> set to all longhand properties
 that are <a href="#supported-css-property" title="supported CSS property">supported CSS properties</a> with the value being the <a href="#computed-value">computed value</a>
 computed for the <a class="external" data-anolis-spec="dom" href="http://dom.spec.whatwg.org/#context-object">context object</a> using the style rules associated
 with the <a class="external" data-anolis-spec="dom" href="http://dom.spec.whatwg.org/#context-object">context object</a>'s <a href="#associated-document">associated document</a>.</p>
 
-<p class="atrisk">The <dfn id="dom-getstyleutils-usedstyle" title="dom-GetStyleUtils-usedStyle"><code>usedStyle</code></dfn> attribute must return a new <a href="#css-declaration-block">CSS declaration block</a> with the
+<p class="atrisk">The <dfn id="dom-getstyleutils-usedstyle" title="dom-GetStyleUtils-usedStyle"><code>usedStyle</code></dfn> attribute must return a <a href="#css-declaration-block">CSS declaration block</a> with the
 <a href="#concept-css-declaration-block-readonly-flag" title="concept-css-declaration-block-readonly-flag">readonly flag</a> set and the
 <a href="#concept-css-declaration-block-declarations" title="concept-css-declaration-block-declarations">declarations</a> set to all longhand properties
 that are <a href="#supported-css-property" title="supported CSS property">supported CSS properties</a> with the value being the <a href="#used-value">used value</a>

cssom/Overview.src.html

@@ -2732,35 +2732,35 @@ <h3>The <code title>GetStyleUtils</code> Interface</h3>
 
 <pre class=idl>[NoInterfaceObject]
 interface <dfn>GetStyleUtils</dfn> {
-  readonly attribute <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-cascadedStyle>cascadedStyle</span>;
-  <!--readonly attribute <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-defaultStyle>defaultStyle</span>;
-  -->readonly attribute <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-rawComputedStyle>rawComputedStyle</span>;
-  readonly attribute <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-usedStyle>usedStyle</span>;
+  [NewObject] <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-cascadedStyle>cascadedStyle</span>();
+  <!--[NewObject] <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-defaultStyle>defaultStyle</span>();
+  -->[NewObject] <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-rawComputedStyle>rawComputedStyle</span>();
+  [NewObject] <span>CSSStyleDeclaration</span> <span title=dom-GetStyleUtils-usedStyle>usedStyle</span>();
 };</pre>
 
-<p class=atrisk>The <dfn title=dom-GetStyleUtils-cascadedStyle><code>cascadedStyle</code></dfn> attribute must return a new <span>CSS declaration block</span>
+<p class=atrisk>The <dfn title=dom-GetStyleUtils-cascadedStyle><code>cascadedStyle</code></dfn> attribute must return a <span>CSS declaration block</span>
 with the <span title=concept-css-declaration-block-readonly-flag>readonly flag</span> set and the
 <span title=concept-css-declaration-block-declarations>declarations</span> set to all longhand properties
 that are <span title="supported CSS property">supported CSS properties</span> that have a <span>cascaded value</span> for the <span data-anolis-spec=dom>context
 object</span>, with the value being the <span>cascaded value</span> computed for the <span data-anolis-spec=dom>context object</span> using the style rules
 associated with the <span data-anolis-spec=dom>context object</span>'s <span>associated document</span>.</p>
 
-<!--<p class=atrisk>The <dfn title=dom-GetStyleUtils-defaultStyle><code>defaultStyle</code></dfn> attribute must return a new <span>CSS declaration block</span> with
-the <span title=concept-css-declaration-block-readonly-flag>readonly flag</span> set and the
+<!--<p class=atrisk>The <dfn title=dom-GetStyleUtils-defaultStyle><code>defaultStyle</code></dfn> attribute must return a <span>CSS declaration block</span>
+with the <span title=concept-css-declaration-block-readonly-flag>readonly flag</span> set and the
 <span title=concept-css-declaration-block-declarations>declarations</span> set to all longhand properties that are
 <span title="supported CSS property">supported CSS properties</span> with the value being the
 <span>computed value</span> computed for the <span data-anolis-spec=dom>context object</span> using the user-agent-level style rules and user-level style rules
 associated with the <span data-anolis-spec=dom>context object</span>'s <span>associated document</span>, ignoring transitions, animations, author-level style
 rules, author-level presentational hints and override-level style rules.</p>-->
 
-<p class=atrisk>The <dfn title=dom-GetStyleUtils-rawComputedStyle><code>rawComputedStyle</code></dfn> attribute must return a new <span>CSS declaration
+<p class=atrisk>The <dfn title=dom-GetStyleUtils-rawComputedStyle><code>rawComputedStyle</code></dfn> attribute must return a <span>CSS declaration
 block</span> with the <span title=concept-css-declaration-block-readonly-flag>readonly flag</span> set and the
 <span title=concept-css-declaration-block-declarations>declarations</span> set to all longhand properties
 that are <span title="supported CSS property">supported CSS properties</span> with the value being the <span>computed value</span>
 computed for the <span data-anolis-spec=dom>context object</span> using the style rules associated
 with the <span data-anolis-spec=dom>context object</span>'s <span>associated document</span>.</p>
 
-<p class=atrisk>The <dfn title=dom-GetStyleUtils-usedStyle><code>usedStyle</code></dfn> attribute must return a new <span>CSS declaration block</span> with the
+<p class=atrisk>The <dfn title=dom-GetStyleUtils-usedStyle><code>usedStyle</code></dfn> attribute must return a <span>CSS declaration block</span> with the
 <span title=concept-css-declaration-block-readonly-flag>readonly flag</span> set and the
 <span title=concept-css-declaration-block-declarations>declarations</span> set to all longhand properties
 that are <span title="supported CSS property">supported CSS properties</span> with the value being the <span>used value</span>