Make sure feedback app footer buttons stick to the bottom

chrome/browser/resources/feedback/css/feedback.css

 /* Copyright 2013 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. */
 
 
 html {
   height: 100%;
 }
 
 body {
   background-color: #fbfbfb;
+  display: flex;
+  flex-direction: column;
   height: 100%;
   margin: 0;
   overflow: auto;
   padding: 0;
   width: 100%;
 }
 
 [hidden] {
   display: none !important;
 }
@@ skipping 13 matching lines @@
   -webkit-flex: 1 1 auto;
   -webkit-margin-start: 20px;
 }
 
 .title-bar .button-bar {
   -webkit-flex: 0 1 auto;
 }
 
 .content {
   color: #646464;
+  flex-grow: 1;
   font-size: 12px;
   margin: 20px;
 }
 
 .content #description-text {
   border-color: #c8c8c8;
   box-sizing: border-box;
   height: 120px;
   line-height: 18px;
   padding: 10px;
@@ skipping 84 matching lines @@
   line-height: 15px;
   margin-bottom: 20px;
   margin-top: 20px;
 }
 
 .content .buttons-pane {
   bottom: 20px;
   display: -webkit-flex;
   justify-content: flex-end;
   left: 20px;
+  position: absolute;
   right: 20px;
 }
 
 .content .top-buttons {
   position: absolute;
 }
 
 .content .remove-file-button {
   -webkit-margin-start: 5px;
   background-color: transparent;
@@ skipping 48 matching lines @@
   height: 50px;
   margin-bottom: 20px;
   margin-top: 120px;
 }
 
 .srt-body {
   font-size: 14px;
   line-height: 24px;
   margin: 0 40px;
 }