Make event_firing_test.html pass in Firefox 24 ESR.

Moving asserts to tests' main flow
in 03feed0
revealed the fact that it never passed in Firefox 24 ESR
(apparently it swallows exceptions thrown from the event handlers?).

Author: sevaseva

javascript/selenium-atoms/test/event_firing_test.html

@@ -32,12 +32,21 @@
         var SUBPIXEL_PRECISION_SUPPORTED = !CLICKING_WITH_COORDINATES_BROKEN &&
             !goog.userAgent.product.CHROME && !goog.userAgent.product.FIREFOX;
 
-        function expectedCoordinate(num) {
+        function expectedEventCoordinate(elementTopLeftCorner, offset) {
+          // TODO: Delete next 'if' statement when Selenium stops supporting Firefox 24 ESR.
+          if (goog.userAgent.product.FIREFOX &&
+              bot.userAgent.isProductVersion(24) &&
+              !bot.userAgent.isProductVersion(25)) {
+            // Firefox 24 ESR events have coordinates of the offset
+            // (relative to top-left corner of the element; not of the viewport).
+            return offset;
+          }
+
           if (SUBPIXEL_PRECISION_SUPPORTED) {
-            return num;
+            return elementTopLeftCorner + offset;
           } else {
             // When browser doesn't support subpixel (for event coords) it truncates to integers.
-            return Math.floor(num);
+            return Math.floor(elementTopLeftCorner + offset);
           }
         }
 
@@ -96,8 +105,8 @@
               'id=location', 'mouseup', offsetX + ',' + offsetY);
 
           assertTrue(fired);
-          assertEquals(expectedCoordinate(clickLocation.left + offsetX), eventClientX);
-          assertEquals(expectedCoordinate(clickLocation.top + offsetY), eventClientY);
+          assertEquals(expectedEventCoordinate(clickLocation.left, offsetX), eventClientX);
+          assertEquals(expectedEventCoordinate(clickLocation.top, offsetY), eventClientY);
         }
 
         function testFiringEventsAtAParticularLocationWillDefaultToTopLeft() {
@@ -118,8 +127,8 @@
           core.events.fireAt('id=location', goog.events.EventType.MOUSEUP);
 
           assertTrue(fired);
-          assertEquals(expectedCoordinate(clickLocation.left), eventClientX);
-          assertEquals(expectedCoordinate(clickLocation.top), eventClientY);
+          assertEquals(expectedEventCoordinate(clickLocation.left, 0), eventClientX);
+          assertEquals(expectedEventCoordinate(clickLocation.top, 0), eventClientY);
         }
 
         function testCanOverrideTheValueOfAnInputElement() {