[MD Bookmarks] Make drag and drop update data model.

chrome/browser/resources/md_bookmarks/dnd_manager.js

Index: chrome/browser/resources/md_bookmarks/dnd_manager.js
diff --git a/chrome/browser/resources/md_bookmarks/dnd_manager.js b/chrome/browser/resources/md_bookmarks/dnd_manager.js
index 5304a097925c4814a01d081614ccf30334d34101..2dfe8b57bfa29ca26b2a3f9eefc509ed599a3a28 100644
--- a/chrome/browser/resources/md_bookmarks/dnd_manager.js
+++ b/chrome/browser/resources/md_bookmarks/dnd_manager.js
@@ -283,13 +283,49 @@ cr.define('bookmarks', function() {
      * @param {!Event} e
      */
     onDrop_: function(e) {
-      if (this.dropDestination_)
+      if (this.dropDestination_) {
         e.preventDefault();
 
+        var dropInfo = this.calculateDropInfo_(this.dropDestination_);
+        if (dropInfo.index != -1)
+          chrome.bookmarkManagerPrivate.drop(dropInfo.parentId, dropInfo.index);
+        else
+          chrome.bookmarkManagerPrivate.drop(dropInfo.parentId);
+      }
+
       this.dropDestination_ = null;
       this.dropIndicator_.finish();
     },
 
+    /**
+     * @param {DropDestination} dropDestination
+     * @return {{parentId: string, index: number}}
+     */
+    calculateDropInfo_: function(dropDestination) {
+      var node = getBookmarkNode(dropDestination.element);
+      var position = dropDestination.position;
+      var index = -1;
+      var parentId = node.id;
+
+      if (position != DropPosition.ON) {
+        var state = bookmarks.Store.getInstance().data;
+
+        // Drops between items in the normal list and the sidebar use the drop
+        // destination node's parent.
+        parentId = node.parentId || '';

[tsergeant, 2017/03/30 04:02:15]

Nit: Maybe assert(node.parentId) here, instead of defaulting to the empty
string.

The end result is the same (since the empty string will just error on the line
below), but the behavior is slightly nicer.

[calamity, 2017/04/03 03:02:28]

Done.

+        index = state.nodes[parentId].children.indexOf(node.id);
+
+        // TODO(calamity): Handle dropping to an empty bookmark list.
+        if (position == DropPosition.BELOW)
+          index++;
+      }
+
+      return {
+        index: index,
+        parentId: parentId,
+      };
+    },
+
     /** @private */
     clearDragData_: function() {
       this.dragInfo_.clearDragData();