[MD Bookmarks] Add drag and drop indicator.

chrome/browser/resources/md_bookmarks/dnd_chip.js

Index: chrome/browser/resources/md_bookmarks/dnd_chip.js
diff --git a/chrome/browser/resources/md_bookmarks/dnd_chip.js b/chrome/browser/resources/md_bookmarks/dnd_chip.js
new file mode 100644
index 0000000000000000000000000000000000000000..41bd9426dba3e8f562413820a23bddf2b676b6b8
--- /dev/null
+++ b/chrome/browser/resources/md_bookmarks/dnd_chip.js
@@ -0,0 +1,44 @@
+// Copyright 2017 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.
+
+Polymer({
+  is: 'bookmarks-dnd-chip',
+
+  properties: {
+    /** @private */
+    showing_: {
+      type: Boolean,
+      reflectToAttribute: true,
+    },
+
+    /** @private */
+    isFolder_: Boolean,
+  },
+
+  /**
+   * @param {number} x
+   * @param {number} y
+   * @param {!Array<BookmarkNode>} items
+   */
+  showForItems: function(x, y, items) {
+    this.style.setProperty('--mouse-x', x + 'px');
+    this.style.setProperty('--mouse-y', y + 'px');
+
+    if (this.showing_)
+      return;
+
+    var firstItem = items[0];
+    this.isFolder_ = !firstItem.url;
+    // TODO(calamity): handle multi-item UI.
+    if (firstItem.url)
+      this.$.icon.style.backgroundImage = cr.icon.getFavicon(firstItem.url);
+
+    this.$.title.textContent = firstItem.title;
+    this.showing_ = true;
+  },
+
+  hide: function() {
+    this.showing_ = false;
+  },
+});