Moving where I'm doing dropEffect normalization.

chrome/browser/resources/ntp4/tile_page.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('ntp4', function() {
   'use strict';
 
   // We can't pass the currently dragging tile via dataTransfer because of
   // http://crbug.com/31037
   var currentlyDraggingTile = null;
   function getCurrentlyDraggingTile() {
     return currentlyDraggingTile;
   }
   function setCurrentlyDraggingTile(tile) {
     currentlyDraggingTile = tile;
     if (tile)
       ntp4.enterRearrangeMode();
     else
       ntp4.leaveRearrangeMode();
   }
 
   /**
+   * Changes the current dropEffect of a drag. This modifies the native cursor
+   * and serves as an indicator of what we should do at the end of the drag as
+   * well as give indication to the user if a drop would succeed if they let go.
+   * @param {DataTransfer} dataTransfer A dataTransfer object from a drag event.
+   * @param {string} effect A drop effect to change to (i.e. copy, move, none).
+   */
+  function setCurrentDropEffect(dataTransfer, effect) {
+    dataTransfer.dropEffect = effect;
+    if (currentlyDraggingTile)
+      currentlyDraggingTile.lastDropEffect = dataTransfer.dropEffect;
+  }
+
+  /**
    * Creates a new Tile object. Tiles wrap content on a TilePage, providing
    * some styling and drag functionality.
    * @constructor
    * @extends {HTMLDivElement}
    */
   function Tile(contents) {
     var tile = cr.doc.createElement('div');
     tile.__proto__ = Tile.prototype;
     tile.initialize(contents);
 
@@ skipping 121 matching lines @@
       var tilePage = this.tilePage;
       if (tilePage)
         tilePage.positionTile_(this.index);
 
       // Take an appropriate action with the drag clone.
       if (this.landedOnTrash) {
         this.dragClone.classList.add('deleting');
       } else if (tilePage) {
         // TODO(dbeam): Until we fix dropEffect to the correct behavior it will
         // differ on windows - crbug.com/39399.  That's why we use the custom
-        // tilePage.lastDropEffect_ instead of e.dataTransfer.dropEffect.
-        if (tilePage.selected && tilePage.lastDropEffect_ != 'copy') {
+        // this.lastDropEffect instead of e.dataTransfer.dropEffect.
+        if (tilePage.selected && this.lastDropEffect != 'copy') {
           // The drag clone can still be hidden from the last drag move event.
           this.dragClone.hidden = false;
           // The tile's contents may have moved following the respositioning;
           // adjust for that.
           var contentDiffX = this.dragClone.firstChild.offsetLeft -
               this.firstChild.offsetLeft;
           var contentDiffY = this.dragClone.firstChild.offsetTop -
               this.firstChild.offsetTop;
           this.dragClone.style.left = (this.gridX + this.parentNode.offsetLeft -
               contentDiffX) + 'px';
           this.dragClone.style.top =
               (this.gridY + this.parentNode.getBoundingClientRect().top -
               contentDiffY) + 'px';
         } else if (this.dragClone.hidden) {
           this.finalizeDrag_();
         } else {
           this.dragClone.classList.add('dropped-on-other-page');
         }
       }
 
+      delete this.lastDropEffect;
       this.landedOnTrash = false;
     },
 
     /**
      * Creates a clone of this node offset by the coordinates. Used for the
      * dragging effect where a tile appears to float off one side of the grid
      * and re-appear on the other.
      * @param {number} x x-axis offset, in pixels.
      * @param {number} y y-axis offset, in pixels.
      */
@@ skipping 731 matching lines @@
      * @param {Event} e A mouseover event for the drag over.
      */
     doDragOver: function(e) {
       e.preventDefault();
 
       this.setDropEffect(e.dataTransfer);
       var newDragIndex = this.getWouldBeIndexForPoint_(e.pageX, e.pageY);
       if (newDragIndex < 0 || newDragIndex >= this.tileElements_.length)
         newDragIndex = this.dragItemIndex_;
       this.updateDropIndicator_(newDragIndex);
-
-      this.lastDropEffect_ = e.dataTransfer.dropEffect;
     },
 
     /**
      * Performs all actions necessary when the user completes a drop.
      * @param {Event} e A mouseover event for the drag drop.
      */
     doDrop: function(e) {
       e.stopPropagation();
 
       var index = this.currentDropIndex_;
@@ skipping 118 matching lines @@
      * 'copy').
      * @param {Object} dataTransfer The drag event dataTransfer object.
      */
     setDropEffect: function(dataTransfer) {
       assert(false);
     },
   };
 
   return {
     getCurrentlyDraggingTile: getCurrentlyDraggingTile,
+    setCurrentDropEffect: setCurrentDropEffect,
     TilePage: TilePage,
   };
 });