diff --git a/core/misc/displace.js b/core/misc/displace.js
index 72a081c..3f96645 100644
--- a/core/misc/displace.js
+++ b/core/misc/displace.js
@@ -1,5 +1,5 @@
 /**
- *
+ * Manages elements that can offset the size of the viewport.
  */
 (function (window, Drupal, $) {
 
@@ -101,7 +101,7 @@
             }
             // If the offset data attribute contains a displacing value, use it.
             var value = parseInt($el.attr('data-offset-' + edge), 10);
-            if (typeof value === 'number') {
+            if (typeof value === 'number' && !isNaN(value)) {
               displacement += value;
             }
             // If the element's offset data attribute does not contain a value,
diff --git a/core/modules/overlay/overlay-child.js b/core/modules/overlay/overlay-child.js
index 2de73e0..60964c8 100644
--- a/core/modules/overlay/overlay-child.js
+++ b/core/modules/overlay/overlay-child.js
@@ -54,15 +54,6 @@ Drupal.behaviors.overlayChild = {
       parent.Drupal.overlay.refreshRegions(settings.refreshRegions);
     }
 
-    // Workaround because of the way jQuery events works.
-    // jQuery from the parent frame needs to be used to catch this event.
-    parent.jQuery(document).on({
-      'drupalViewportOffsetChange': function (event, offsets) {
-        // Fires an event that the child iframe can listen to.
-        $(document).trigger('drupalViewportOffsetChange', offsets);
-      }
-    });
-
     // Ok, now we can tell the parent window we're ready.
     parent.Drupal.overlay.bindChild(window);
 
diff --git a/core/modules/overlay/overlay-parent.js b/core/modules/overlay/overlay-parent.js
index fbe1e7f..52de4b4 100644
--- a/core/modules/overlay/overlay-parent.js
+++ b/core/modules/overlay/overlay-parent.js
@@ -144,11 +144,9 @@ Drupal.overlay.create = function () {
           ' drupalOverlayBeforeLoad' + eventClass +
           ' drupalOverlayResize' + eventClass, $.proxy(this, 'eventhandlerDispatchEvent'));
 
-  if (Drupal.displace.getElements().top.length || Drupal.displace.getElements().bottom.length) {
-    $(document)
-      .bind('drupalOverlayResize' + eventClass, $.proxy(this, 'eventhandlerAlterDisplacedElements'))
-      .bind('drupalOverlayClose' + eventClass, $.proxy(this, 'eventhandlerRestoreDisplacedElements'));
-  }
+  $(document)
+    .bind('drupalOverlayResize' + eventClass, $.proxy(this, 'eventhandlerAlterDisplacedElements'))
+    .bind('drupalOverlayClose' + eventClass, $.proxy(this, 'eventhandlerRestoreDisplacedElements'));
 };
 
 /**
@@ -464,6 +462,12 @@ Drupal.overlay.eventhandlerAlterDisplacedElements = function (event) {
   // IE6 doesn't support maxWidth, use width instead.
   var maxWidthName = 'maxWidth';
 
+  // If either the documentWidth or documentHeight are a zero dimension, abort
+  // the effort to alter presentation elements.
+  if (documentWidth === 0 || documentHeight === 0) {
+    return;
+  }
+
   if (Drupal.overlay.leftSidedScrollbarOffset === undefined && $(document.documentElement).attr('dir') === 'rtl') {
     // We can't use element.clientLeft to detect whether scrollbars are placed
     // on the left side of the element when direction is set to "rtl" as most
@@ -487,7 +491,7 @@ Drupal.overlay.eventhandlerAlterDisplacedElements = function (event) {
 
   // Consider any element that should be visible above the overlay (such as
   // a toolbar).
-  $('.overlay-displace-top, .overlay-displace-bottom').each(function () {
+  $(Drupal.displace.getElements().top).add(Drupal.displace.getElements().bottom).each(function () {
     var data = $(this).data();
     var maxWidth = documentWidth;
     // In IE, Shadow filter makes element to overlap the scrollbar with 1px.
diff --git a/core/modules/toolbar/js/toolbar.js b/core/modules/toolbar/js/toolbar.js
index 267f1b6..33c7133 100644
--- a/core/modules/toolbar/js/toolbar.js
+++ b/core/modules/toolbar/js/toolbar.js
@@ -190,6 +190,9 @@ Drupal.toolbar.setHeight = function () {
   /**
    * Get the height of the active tray and include it in the total
    * height of the toolbar.
+   *
+   * If the height of the bar changed, Drupal.displace is called so that
+   * elements can adjust to the placement of the bar.
    */
   height += $trays.filter('.active.horizontal').outerHeight() || 0;
   // Indicate the height of the toolbar in the attribute data-offset-top.
@@ -203,6 +206,12 @@ Drupal.toolbar.setHeight = function () {
   }
 };
 
+/**
+ * Sets the width of a vertical tray in a data attribute.
+ *
+ * If the width of the tray changed, Drupal.displace is called so that elements
+ * can adjust to the placement of the tray.
+ */
 Drupal.toolbar.setTrayWidth = function () {
   var $tray = $toolbar.find('.tray.active');
   var trayWidth = $tray.hasClass('vertical') ? $tray.width() : 0;