Bug 1199023. Fix expectations of widget/tests/test_native_key_bindings_mac.html when a scrollbar is added to the iframe it is run in. r=jryans

The scrollbar changes when the test wraps, and so an operation that deletes text until the end of line deletes a different amount of text, and thus affects where the end of line is after the delete.

widget/tests/test_native_key_bindings_mac.html

@@ -265,7 +265,7 @@
       synthesizedKeys.push([KEYBOARD_LAYOUT_EN_US, MAC_VK_ANSI_E,
                             {ctrlKey: true}, "\u0005", "e"]);
       expectations.push({
-        editable: [144, 144],
+        editable: [139, 139],
         textarea: [94, 94],
         input:    [17, 17]
       });