ntp4: app install improvements

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;
@@ skipping 143 matching lines @@
       setCurrentlyDraggingTile(null);
 
       // tilePage will be null if we've already been removed.
       if (this.tilePage)
         this.tilePage.positionTile_(this.index);
 
       // Take an appropriate action with the drag clone.
       if (this.landedOnTrash) {
         this.dragClone.classList.add('deleting');
       } else if (this.tilePage) {
-        if (this.tilePage.selected) {
+        if (this.tilePage.selected && e.dataTransfer.dropEffect != 'copy') {
           // 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 -
@@ skipping 721 matching lines @@
     },
 
     /**
      * Performs all actions necessary when the user moves the cursor during
      * a drag over the tile page.
      * @param {Event} e A mouseover event for the drag over.
      */
     doDragOver: function(e) {
       e.preventDefault();
 
-      if (currentlyDraggingTile)
-        e.dataTransfer.dropEffect = 'move';
-      else
-        e.dataTransfer.dropEffect = 'copy';
-
+      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);
     },
 
     /**
      * Performs all actions necessary when the user completes a drop.
      * @param {Event} e A mouseover event for the drag drop.
      */
@@ skipping 102 matching lines @@
       assert(false);
     },
 
     /**
      * Called when a tile has been moved (via dragging). Override this to make
      * backend updates.
      * @param {Node} draggedTile The tile that was dropped.
      */
     tileMoved: function(draggedTile) {
     },
+
+    /**
+     * Sets the drop effect on |dataTransfer| to the desired value (e.g.
+     * 'copy').
+     * @param {Object} dataTransfer The drag event dataTransfer object.
+     */
+    setDropEffect: function(dataTransfer) {
+      assert(false);
+    },
   };
 
   return {
     getCurrentlyDraggingTile: getCurrentlyDraggingTile,
     TilePage: TilePage,
   };
 });