Make all elements query test helpers return the client's top and left

These test helpers return an element's getBoundingClientRect width and
height only. Include the DOMRect .top and .left as well [1].

[1] Useful for table mode + touch event testing, should be the same as
W3C DOMRect .x and .y values. Would prefer those, but closure does not
define them [2] whereas the W3C DOM specs do.

[2] Filed https://github.com/google/closure-compiler/issues/3140

Bug: 839243
Change-Id: I0cce0e4a121fd7bca49645d09e98d013fbf920f0
Reviewed-on: https://chromium-review.googlesource.com/c/1325270
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606322}

ui/file_manager/file_manager/background/js/test_util_base.js

@@ -48,13 +48,17 @@ function extractElementInfo(element, contentWindow, opt_styleNames) {
   }
 
   result.styles = styles;
-  // These attributes are set when element is img or canvas.
+
+  // These attributes are set when element is <img> or <canvas>.
   result.imageWidth = Number(element.width);
   result.imageHeight = Number(element.height);
 
   // These attributes are set in any element.
   result.renderedWidth = size.width;
   result.renderedHeight = size.height;
+  result.renderedTop = size.top;
+  result.renderedLeft = size.left;
+
   return result;
 }