dojo/dom-geometry.position(node, true) wrong on zoomed android device

[bill]

While most dojo/dom-geometry methods like position(node) return the coordinates relative to the layout viewport (i.e. the viewport before pinch-zoom), docScroll() returns the scroll of the visual viewport (i.e. what is shown on the screen after pinch zoom).

Besides the inconsistency, this behavior breaks position(node, true) and subsequently placement of dropdowns (see #18454).

This problem is caused by a Chrome/Android? "bug" where document.scrollLeft and document.scrollTop are the scroll of the visual viewport rather than the layout viewport.

As explained in ​https://code.google.com/p/chromium/issues/detail?id=489206#c19, the workaround is to change docScroll() to create a <div id=pagetopelement style="position:absolute;left:0;top:0"> and then call pagetopelement.getBoundingClientRect() on that <div>.

Based on dijit ticket #18454 but filing this ticket since it's really a core issue.

[bill]

#18753 is a duplicate of this ticket.

[dylan]

Want to file a pull request for 1.11? Otherwise I'll look at this for 1.12.