[cssom-view] Elements with overflow:scroll has a scrolling box even if there's no overflow. https://www.w3.org/Bugs/Public/show_bug.cgi?id=23607

Author: Simon Pieters

cssom-view/Overview.html

@@ -240,8 +240,8 @@ <h2 id="terminology"><span class="secno">3 </span>Terminology</h2>
 
 <p><dfn id="block-flow-direction">Block flow direction</dfn> and <dfn id="inline-base-direction">inline base direction</dfn> are defined in CSS Writing Modes Module. <a href="#refsCSSWRITINGMODES">[CSSWRITINGMODES]</a>
 
-<p>Elements and <a href="#viewport" title="viewport">viewports</a> have an associated <dfn id="scrolling-box">scrolling box</dfn> if it overflows its content area<!--XXX xref--> and either has
-a scrolling mechanism<!--XXX xref--> or the used value of the 'overflow-x' or 'overflow-y' property is 'hidden'. <a href="#refsCSSBOX">[CSSBOX]</a>
+<p>Elements and <a href="#viewport" title="viewport">viewports</a> have an associated <dfn id="scrolling-box">scrolling box</dfn> if has a scrolling mechanism<!--XXX xref--> or it overflows
+its content area<!--XXX xref--> and the used value of the 'overflow-x' or 'overflow-y' property is 'hidden'. <a href="#refsCSSBOX">[CSSBOX]</a>
 
 <p>A <a href="#scrolling-box">scrolling box</a> of a <a href="#viewport">viewport</a> or element has two <dfn id="overflow-directions">overflow directions</dfn>, depending on the <a href="#viewport">viewport</a>'s or
 element's <a href="#block-flow-direction">block flow direction</a> and <a href="#inline-base-direction">inline base direction</a>, as follows:

cssom-view/Overview.src.html

@@ -197,8 +197,8 @@ <h2>Terminology</h2>
 
 <p><dfn>Block flow direction</dfn> and <dfn>inline base direction</dfn> are defined in CSS Writing Modes Module. <span data-anolis-ref>CSSWRITINGMODES</span>
 
-<p>Elements and <span title=viewport>viewports</span> have an associated <dfn>scrolling box</dfn> if it overflows its content area<!--XXX xref--> and either has
-a scrolling mechanism<!--XXX xref--> or the used value of the 'overflow-x' or 'overflow-y' property is 'hidden'. <span data-anolis-ref>CSSBOX</span>
+<p>Elements and <span title=viewport>viewports</span> have an associated <dfn>scrolling box</dfn> if has a scrolling mechanism<!--XXX xref--> or it overflows
+its content area<!--XXX xref--> and the used value of the 'overflow-x' or 'overflow-y' property is 'hidden'. <span data-anolis-ref>CSSBOX</span>
 
 <p>A <span>scrolling box</span> of a <span>viewport</span> or element has two <dfn>overflow directions</dfn>, depending on the <span>viewport</span>'s or
 element's <span>block flow direction</span> and <span>inline base direction</span>, as follows: