MD downloads: update toolbar styles

chrome/browser/resources/md_downloads/manager.css

 /* Copyright 2015 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. */
 
 :host {
   @apply(--downloads-shared-style);
   display: flex;
   flex: 1 0;
   flex-direction: column;
   height: 100%;
 }
 
 @media screen and (max-width: 1024px) {
   :host {
     flex-basis: 670px;
   }
 }
 
 #panel {
   --paper-header-panel-standard-container: {
     display: flex;
   };
 }
 
+/* TODO(dbeam): upgrade to 1.0.4 to use --paper-header-panel-shadow.
+ * https://github.com/PolymerElements/paper-header-panel/pull/39 */
+#panel /deep/ #dropShadow {
+  display: none;
+}
+
 #no-downloads,
 #downloads-list {
   flex: 1;
 }
 
 .loading :-webkit-any(#no-downloads, #downloads-list) {
   display: none;
 }
 
 #no-downloads {
   align-items: center;
   color: #b4b4b4;
   display: flex;
   font-size: 107.69%;
   justify-content: center;
 }
 
 #no-downloads .illustration {
   content: -webkit-image-set(url(1x/no_downloads.png) 1x,
                              url(2x/no_downloads.png) 2x);
   margin-bottom: 32px;
 }