diff -r 000000000000 -r 6474c204b198 browser/base/content/newtab/cells.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/newtab/cells.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,126 @@
+#ifdef 0
+/* 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/. */
+#endif
+
+/**
+ * This class manages a cell's DOM node (not the actually cell content, a site).
+ * It's mostly read-only, i.e. all manipulation of both position and content
+ * aren't handled here.
+ */
+function Cell(aGrid, aNode) {
+  this._grid = aGrid;
+  this._node = aNode;
+  this._node._newtabCell = this;
+
+  // Register drag-and-drop event handlers.
+  ["dragenter", "dragover", "dragexit", "drop"].forEach(function (aType) {
+    this._node.addEventListener(aType, this, false);
+  }, this);
+}
+
+Cell.prototype = {
+  /**
+   * The grid.
+   */
+  _grid: null,
+
+  /**
+   * The cell's DOM node.
+   */
+  get node() this._node,
+
+  /**
+   * The cell's offset in the grid.
+   */
+  get index() {
+    let index = this._grid.cells.indexOf(this);
+
+    // Cache this value, overwrite the getter.
+    Object.defineProperty(this, "index", {value: index, enumerable: true});
+
+    return index;
+  },
+
+  /**
+   * The previous cell in the grid.
+   */
+  get previousSibling() {
+    let prev = this.node.previousElementSibling;
+    prev = prev && prev._newtabCell;
+
+    // Cache this value, overwrite the getter.
+    Object.defineProperty(this, "previousSibling", {value: prev, enumerable: true});
+
+    return prev;
+  },
+
+  /**
+   * The next cell in the grid.
+   */
+  get nextSibling() {
+    let next = this.node.nextElementSibling;
+    next = next && next._newtabCell;
+
+    // Cache this value, overwrite the getter.
+    Object.defineProperty(this, "nextSibling", {value: next, enumerable: true});
+
+    return next;
+  },
+
+  /**
+   * The site contained in the cell, if any.
+   */
+  get site() {
+    let firstChild = this.node.firstElementChild;
+    return firstChild && firstChild._newtabSite;
+  },
+
+  /**
+   * Checks whether the cell contains a pinned site.
+   * @return Whether the cell contains a pinned site.
+   */
+  containsPinnedSite: function Cell_containsPinnedSite() {
+    let site = this.site;
+    return site && site.isPinned();
+  },
+
+  /**
+   * Checks whether the cell contains a site (is empty).
+   * @return Whether the cell is empty.
+   */
+  isEmpty: function Cell_isEmpty() {
+    return !this.site;
+  },
+
+  /**
+   * Handles all cell events.
+   */
+  handleEvent: function Cell_handleEvent(aEvent) {
+    // We're not responding to external drag/drop events
+    // when our parent window is in private browsing mode.
+    if (inPrivateBrowsingMode() && !gDrag.draggedSite)
+      return;
+
+    if (aEvent.type != "dragexit" && !gDrag.isValid(aEvent))
+      return;
+
+    switch (aEvent.type) {
+      case "dragenter":
+        aEvent.preventDefault();
+        gDrop.enter(this, aEvent);
+        break;
+      case "dragover":
+        aEvent.preventDefault();
+        break;
+      case "dragexit":
+        gDrop.exit(this, aEvent);
+        break;
+      case "drop":
+        aEvent.preventDefault();
+        gDrop.drop(this, aEvent);
+        break;
+    }
+  }
+};