[MD Bookmarks] Add draggable sidebar.

chrome/browser/resources/md_bookmarks/toolbar.js

Index: chrome/browser/resources/md_bookmarks/toolbar.js
diff --git a/chrome/browser/resources/md_bookmarks/toolbar.js b/chrome/browser/resources/md_bookmarks/toolbar.js
index 5b80c74fbef76ca922d66d67cd7c0c724778a044..ebac378331a9e844c80673408e68ba9af137e529 100644
--- a/chrome/browser/resources/md_bookmarks/toolbar.js
+++ b/chrome/browser/resources/md_bookmarks/toolbar.js
@@ -10,6 +10,11 @@ Polymer({
       type: String,
       observer: 'onSearchTermChanged_',
     },
+
+    sidebarWidth: {
+      type: String,
+      observer: 'onSidebarWidthChanged_',
+    },
   },
 
   /** @return {CrToolbarSearchFieldElement} */
@@ -69,6 +74,10 @@ Polymer({
     this.fire('search-term-changed', searchTerm);
   },
 
+  onSidebarWidthChanged_: function() {
+    this.style.setProperty('--sidebar-width', this.sidebarWidth);
+  },
+
   /** @private */
   onSearchTermChanged_: function() {
     this.searchField.setValue(this.searchTerm || '');