[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 6b89342cf60b2116c08b802315b13bf06ec394c7..816ee10df2fa939755451ed790dd82a235fa02bc 100644
--- a/chrome/browser/resources/md_bookmarks/toolbar.js
+++ b/chrome/browser/resources/md_bookmarks/toolbar.js
@@ -15,6 +15,11 @@ Polymer({
       type: String,
       observer: 'onSearchTermChanged_',
     },
+
+    sidebarWidth: {
+      type: String,
+      observer: 'onSidebarWidthChanged_',
+    },
   },
 
   attached: function() {
@@ -80,6 +85,10 @@ Polymer({
     this.dispatch(bookmarks.actions.setSearchTerm(searchTerm));
   },
 
+  onSidebarWidthChanged_: function() {
+    this.style.setProperty('--sidebar-width', this.sidebarWidth);
+  },
+
   /** @private */
   onSearchTermChanged_: function() {
     this.searchField.setValue(this.searchTerm_ || '');