Add overflowY.

Fixes #1892.

std/js/html/CSSStyleDeclaration.hx

@@ -475,9 +475,12 @@ Negative value are also allowed. */
 	/** The<code> overflow </code>CSS property specifies whether to clip content, render scroll bars or display overflow content of a block-level element. */
 	var overflow : String;
 
-	/** The <code>overflow-x </code><a title="CSS" rel="internal" href="https://developer.mozilla.org/en/CSS">CSS</a> property specifies whether to clip content, render a scroll bar or display overflow content of a block-level element, when it overflows at the left and right edges. */
+	/** The <code>overflow-x </code><a title="CSS" rel="internal" href="https://developer.mozilla.org/en/CSS">CSS</a> property specifies whether to clip content, render a scroll bar, or display overflow content of a block-level element, when it overflows at the left and right edges. */
 	var overflowX : String;
 
+	/** The <code>overflow-y </code><a title="CSS" rel="internal" href="https://developer.mozilla.org/en/CSS">CSS</a> property specifies whether to clip content, render a scroll bar, or display overflow content of a block-level element, when it overflows at the top and bottom edges. */
+	var overflowY : String;
+
 	/** The<code> padding </code>CSS property sets the required padding space on all sides of an element. The <a title="http://developer.mozilla.org/en/CSS/Box_model#padding" rel="internal" href="https://developer.mozilla.org/en/CSS/Box_model#padding">padding area</a> is the space between the content of the element and its border. Negative values are not allowed. */
 	var padding : String;