Add UMA metric to track usage of sending a mousedown to select elements.

third_party/WebKit/LayoutTests/imported/wpt/common/canvas-tests.js

 function _valToString(val)
 {
     if (val === undefined || val === null)
         return '[' + typeof(val) + ']';
     return val.toString() + '[' + typeof(val) + ']';
 }
 
 function _assert(cond, text)
 {
     assert_true(!!cond, text);
@@ skipping 66 matching lines @@
     var w = imagedata.width, h = imagedata.height, d = imagedata.data;
     for (var i = 0; i < h; ++i) {
         for (var j = 0; j < w; ++j) {
             testColor(d, 4 * (w * i + j) + 0, 0);
             testColor(d, 4 * (w * i + j) + 1, 255);
             testColor(d, 4 * (w * i + j) + 2, 0);
             testColor(d, 4 * (w * i + j) + 3, 255);
         }
     }
 }
+
+function addCrossOriginYellowImage()
+{
+    var img = new Image();
+    img.id = "yellow.png";
+    img.className = "resource";
+    img.src = get_host_info().HTTP_REMOTE_ORIGIN + "/images/yellow.png";
+    document.body.appendChild(img);
+}