diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_890140_orphaned_placeholders.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_890140_orphaned_placeholders.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,167 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+requestLongerTimeout(2);
+
+// One orphaned item should have two placeholders next to it.
+add_task(function() {
+  yield startCustomizing();
+  let btn = document.getElementById("open-file-button");
+  let panel = document.getElementById(CustomizableUI.AREA_PANEL);
+  let placements = getAreaWidgetIds(CustomizableUI.AREA_PANEL);
+
+  if (isInWin8()) {
+    CustomizableUI.removeWidgetFromArea("switch-to-metro-button");
+    placements = getAreaWidgetIds(CustomizableUI.AREA_PANEL);
+    ok(!CustomizableUI.inDefaultState, "Should no longer be in default state.");
+  } else {
+    ok(CustomizableUI.inDefaultState, "Should be in default state.");
+  }
+
+  assertAreaPlacements(CustomizableUI.AREA_PANEL, placements);
+  is(getVisiblePlaceholderCount(panel), 2, "Should only have 2 visible placeholders before exiting");
+
+  yield endCustomizing();
+  yield startCustomizing();
+  is(getVisiblePlaceholderCount(panel), 2, "Should only have 2 visible placeholders after re-entering");
+
+  if (isInWin8()) {
+    CustomizableUI.addWidgetToArea("switch-to-metro-button", CustomizableUI.AREA_PANEL);
+  }
+  ok(CustomizableUI.inDefaultState, "Should be in default state again.");
+});
+
+// Two orphaned items should have one placeholder next to them (case 1).
+add_task(function() {
+  yield startCustomizing();
+  let btn = document.getElementById("open-file-button");
+  let panel = document.getElementById(CustomizableUI.AREA_PANEL);
+  let placements = getAreaWidgetIds(CustomizableUI.AREA_PANEL);
+
+  let placementsAfterAppend = placements;
+
+  if (!isInWin8()) {
+    placementsAfterAppend = placements.concat(["open-file-button"]);
+    simulateItemDrag(btn, panel);
+  }
+
+  assertAreaPlacements(CustomizableUI.AREA_PANEL, placementsAfterAppend);
+  is(CustomizableUI.inDefaultState, isInWin8(), "Should only be in default state if on Win8");
+  is(getVisiblePlaceholderCount(panel), 1, "Should only have 1 visible placeholder before exiting");
+
+  yield endCustomizing();
+  yield startCustomizing();
+  is(getVisiblePlaceholderCount(panel), 1, "Should only have 1 visible placeholder after re-entering");
+
+  let palette = document.getElementById("customization-palette");
+  simulateItemDrag(btn, palette);
+
+  if (!isInWin8()) {
+    btn = document.getElementById("open-file-button");
+    simulateItemDrag(btn, palette);
+  }
+  ok(CustomizableUI.inDefaultState, "Should be in default state again."); 
+});
+
+// Two orphaned items should have one placeholder next to them (case 2).
+add_task(function() {
+  yield startCustomizing();
+  let btn = document.getElementById("add-ons-button");
+  let btn2 = document.getElementById("developer-button");
+  let btn3 = document.getElementById("switch-to-metro-button");
+  let panel = document.getElementById(CustomizableUI.AREA_PANEL);
+  let palette = document.getElementById("customization-palette");
+  let placements = getAreaWidgetIds(CustomizableUI.AREA_PANEL);
+
+  let placementsAfterAppend = placements.filter(p => p != btn.id && p != btn2.id);
+  simulateItemDrag(btn, palette);
+  simulateItemDrag(btn2, palette);
+
+  if (isInWin8()) {
+    placementsAfterAppend = placementsAfterAppend.filter(p => p != btn3.id);
+    simulateItemDrag(btn3, palette);
+  }
+
+  assertAreaPlacements(CustomizableUI.AREA_PANEL, placementsAfterAppend);
+  ok(!CustomizableUI.inDefaultState, "Should no longer be in default state.");
+  is(getVisiblePlaceholderCount(panel), 1, "Should only have 1 visible placeholder before exiting");
+
+  yield endCustomizing();
+  yield startCustomizing();
+  is(getVisiblePlaceholderCount(panel), 1, "Should only have 1 visible placeholder after re-entering");
+
+  simulateItemDrag(btn, panel);
+  simulateItemDrag(btn2, panel);
+
+  if (isInWin8()) {
+    simulateItemDrag(btn3, panel);
+  }
+
+  assertAreaPlacements(CustomizableUI.AREA_PANEL, placements);
+  ok(CustomizableUI.inDefaultState, "Should be in default state again.");
+});
+
+// A wide widget at the bottom of the panel should have three placeholders after it.
+add_task(function() {
+  yield startCustomizing();
+  let btn = document.getElementById("edit-controls");
+  let developerButton = document.getElementById("developer-button");
+  let metroBtn = document.getElementById("switch-to-metro-button");
+  let panel = document.getElementById(CustomizableUI.AREA_PANEL);
+  let palette = document.getElementById("customization-palette");
+  let placements = getAreaWidgetIds(CustomizableUI.AREA_PANEL);
+
+  placements.pop();
+  simulateItemDrag(developerButton, palette);
+  if (isInWin8()) {
+    // Remove switch-to-metro-button
+    placements.pop();
+    simulateItemDrag(metroBtn, palette);
+  }
+
+  let placementsAfterAppend = placements.concat([placements.shift()]);
+  simulateItemDrag(btn, panel);
+  assertAreaPlacements(CustomizableUI.AREA_PANEL, placementsAfterAppend);
+  ok(!CustomizableUI.inDefaultState, "Should no longer be in default state.");
+  is(getVisiblePlaceholderCount(panel), 3, "Should have 3 visible placeholders before exiting");
+
+  yield endCustomizing();
+  yield startCustomizing();
+  is(getVisiblePlaceholderCount(panel), 3, "Should have 3 visible placeholders after re-entering");
+
+  simulateItemDrag(developerButton, panel);
+  if (isInWin8()) {
+    simulateItemDrag(metroBtn, panel);
+  }
+  let zoomControls = document.getElementById("zoom-controls");
+  simulateItemDrag(btn, zoomControls);
+  ok(CustomizableUI.inDefaultState, "Should be in default state again.");
+});
+
+// The default placements should have two placeholders at the bottom (or 1 in win8).
+add_task(function() {
+  yield startCustomizing();
+  let numPlaceholders = isInWin8() ? 1 : 2;
+  let panel = document.getElementById(CustomizableUI.AREA_PANEL);
+  ok(CustomizableUI.inDefaultState, "Should be in default state.");
+  is(getVisiblePlaceholderCount(panel), numPlaceholders, "Should have " + numPlaceholders + " visible placeholders before exiting");
+
+  yield endCustomizing();
+  yield startCustomizing();
+  is(getVisiblePlaceholderCount(panel), numPlaceholders, "Should have " + numPlaceholders + " visible placeholders after re-entering");
+
+  ok(CustomizableUI.inDefaultState, "Should still be in default state.");
+});
+
+add_task(function asyncCleanup() {
+  yield endCustomizing();
+  yield resetCustomization();
+});
+
+function getVisiblePlaceholderCount(aPanel) {
+  let visiblePlaceholders = aPanel.querySelectorAll(".panel-customization-placeholder:not([hidden=true])");
+  return visiblePlaceholders.length;
+}