[cssom-view] Bail if document is not the active document. Fixes https://www.w3.org/Bugs/Public/show_bug.cgi?id=28488

Author: zcorpan

cssom-view/Overview.bs

@@ -1071,6 +1071,7 @@ The <dfn method for=Element lt="scroll(options)|scroll(x, y)">scroll()</dfn> met
     1. Let the {{ScrollToOptions/left}} dictionary member of <var>options</var> have the value <var>x</var>.
     1. Let the {{ScrollToOptions/top}} dictionary member of <var>options</var> have the value <var>y</var>.
 1. Let <var>document</var> be the element's <a>node document</a>.
+1. If <var>document</var> is not the <a>active document</a>, terminate these steps.
 1. Let <var>window</var> be the value of <var>document</var>'s {{Document/defaultView}} attribute.
 1. If <var>window</var> is null, terminate these steps.
 1. If the element is the root element and <var>document</var> is in <a>quirks mode</a>, terminate these steps.
@@ -1110,6 +1111,7 @@ user agent must run these steps:
 The <dfn attribute for=Element>scrollTop</dfn> attribute, on getting, must return the result of running these steps:
 
 1. Let <var>document</var> be the element's <a>node document</a>.
+1. If <var>document</var> is not the <a>active document</a>, return zero and terminate these steps.
 1. Let <var>window</var> be the value of <var>document</var>'s {{Document/defaultView}} attribute.
 1. If <var>window</var> is null, return zero and terminate these steps.
 1. If the element is the root element and <var>document</var> is in <a>quirks mode</a>, return zero and terminate these steps.
@@ -1123,6 +1125,7 @@ When setting the {{Element/scrollTop}} attribute these steps must be run:
 1. Let <var>y</var> be the given value.
 1. <a>Normalize non-finite values</a> for <var>y</var>.
 1. Let <var>document</var> be the element's <a>node document</a>.
+1. If <var>document</var> is not the <a>active document</a>, terminate these steps.
 1. Let <var>window</var> be the value of <var>document</var>'s {{Document/defaultView}} attribute.
 1. If <var>window</var> is null, terminate these steps.
 1. If the element is the root element and <var>document</var> is in <a>quirks mode</a>, terminate these steps.
@@ -1134,6 +1137,7 @@ When setting the {{Element/scrollTop}} attribute these steps must be run:
 The <dfn attribute for=Element>scrollLeft</dfn> attribute, on getting, must return the result of running these steps:
 
 1. Let <var>document</var> be the element's <a>node document</a>.
+1. If <var>document</var> is not the <a>active document</a>, return zero and terminate these steps.
 1. Let <var>window</var> be the value of <var>document</var>'s {{Document/defaultView}} attribute.
 1. If <var>window</var> is null, return zero and terminate these steps.
 1. If the element is the root element and <var>document</var> is in <a>quirks mode</a>, return zero and terminate these steps.
@@ -1147,6 +1151,7 @@ When setting the {{Element/scrollLeft}} attribute these steps must be run:
 1. Let <var>x</var> be the given value.
 1. <a>Normalize non-finite values</a> for <var>x</var>.
 1. Let <var>document</var> be the element's <a>node document</a>.
+1. If <var>document</var> is not the <a>active document</a>, terminate these steps.
 1. Let <var>window</var> be the value of <var>document</var>'s {{Document/defaultView}} attribute.
 1. If <var>window</var> is null, terminate these steps.
 1. If the element is the root element and <var>document</var> is in <a>quirks mode</a>, terminate these steps.
@@ -1158,6 +1163,7 @@ When setting the {{Element/scrollLeft}} attribute these steps must be run:
 The <dfn attribute for=Element>scrollWidth</dfn> attribute must return the result of running these steps:
 
 1. Let <var>document</var> be the element's <a>node document</a>.
+1. If <var>document</var> is not the <a>active document</a>, return zero and terminate these steps.
 1. Let <var>viewport width</var> be the width of the <a>viewport</a> excluding the width of the scroll bar, if any, or zero if there is no <a>viewport</a>.
 1. If the element is the root element and <var>document</var> is not in <a>quirks mode</a> return max(<a>viewport</a> <a>scrolling area</a> width, <var>viewport width</var>).
 1. If the element is <a>the HTML <code>body</code> element</a>, <var>document</var> is in <a>quirks mode</a> and the element is not <a>potentially scrollable</a>, return max(<a>viewport</a> <a>scrolling area</a> width, <var>viewport width</var>).
@@ -1167,6 +1173,7 @@ The <dfn attribute for=Element>scrollWidth</dfn> attribute must return the resul
 The <dfn attribute for=Element>scrollHeight</dfn> attribute must return the result of running these steps:
 
 1. Let <var>document</var> be the element's <a>node document</a>.
+1. If <var>document</var> is not the <a>active document</a>, return zero and terminate these steps.
 1. Let <var>viewport height</var> be the height of the <a>viewport</a> excluding the height of the scroll bar, if any, or zero if there is no <a>viewport</a>.
 1. If the element is the root element and <var>document</var> is not in <a>quirks mode</a> return max(<a>viewport</a> <a>scrolling area</a> height, <var>viewport height</var>).
 1. If the element is <a>the HTML <code>body</code> element</a>, <var>document</var> is in <a>quirks mode</a> and the element is not <a>potentially scrollable</a>, return max(<a>viewport</a> <a>scrolling area</a> height, <var>viewport height</var>).