Material PDF: Improve layout of PDF viewer in very small windows

chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.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. */
 
 /* We introduce a wrapper aligner element as setting the relevant attributes
  * (horizontal justified layout center) have no effect on the core-toolbar. */
 #aligner {
   width: 100%;
 }
 
@@ skipping 47 matching lines @@
   background: rgba(255, 255, 255, 0.3);
 }
 
 paper-toolbar /deep/ .toolbar-tools {
   height: 48px;
 }
 
 .invisible {
   visibility: hidden;
 }
+
+@media(max-width: 675px) {
+  #bookmarks,
+  #rotate-left {
+    display: none;
+  }
+
+  #pageselector-container {
+    flex: 2;
+  }
+}
+
+@media(max-width: 450px) {
+  #rotate-right {
+    display: none;
+  }
+}
+
+@media(max-width: 400px) {
+  #buttons,
+  #pageselector-container {
+    display: none;
+  }
+}