Have tests verify clientX/Y and pageX/Y properties in drag-and-drop DOM events.

chrome/test/data/drag_and_drop/event_monitoring.js

Index: chrome/test/data/drag_and_drop/event_monitoring.js
diff --git a/chrome/test/data/drag_and_drop/event_monitoring.js b/chrome/test/data/drag_and_drop/event_monitoring.js
index e27cf37f1fe7d58fc3bd2e6dd1c9ad921fe62075..badd6ad9005ea12db5275264a0b67331d480c342 100644
--- a/chrome/test/data/drag_and_drop/event_monitoring.js
+++ b/chrome/test/data/drag_and_drop/event_monitoring.js
@@ -17,6 +17,9 @@ window.reportDragAndDropEvent = function(ev) {
   if (window.domAutomationController) {
     window.domAutomationController.setAutomationId(0);
     window.domAutomationController.send({
+      client_position: safe(function() {
+        return "(" + ev.clientX + ", " + ev.clientY + ")";
+      }),
       drop_effect: safe(function() { return ev.dataTransfer.dropEffect; }),
       effect_allowed: safe(function() {
         return ev.dataTransfer.effectAllowed;
@@ -31,6 +34,9 @@ window.reportDragAndDropEvent = function(ev) {
       mime_types: safe(function() {
         return Array.from(ev.dataTransfer.types).sort().join();
       }),
+      page_position: safe(function() {
+        return "(" + ev.pageX + ", " + ev.pageY + ")";
+      }),
       window_name: window.name
     });
   }