Make Print Preview elements transitions smoother.

chrome/browser/resources/print_preview/print_preview.css

 /* Copyright (c) 2012 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%;
   overflow: hidden;
 }
 
 body {
@@ skipping 60 matching lines @@
 .right-column .radio label {
   padding-bottom: 5px;
   padding-top: 10px;
 }
 
 .right-column .radio input[type='radio'] {
   height: 13px;
   width: 13px;
 }
 
-.two-column h1 {
+.left-column {
   -webkit-padding-end: 20px;
   -webkit-padding-start: 20px;
-  color: #646464;
   display: table-cell;
-  font-size: 12px;
   min-width: 70px;
+  vertical-align: middle;
 }
 
-.two-column.visible h1,
+.left-column h1 {
+  -webkit-margin-after: 0;
+  -webkit-margin-before: 0;
+  color: #646464;
+  font-size: 12px;
+}
+
+.two-column.visible .left-column,
 .two-column.visible .right-column {
   padding-bottom: 5px;
   padding-top: 5px;
 }
 
+.two-column:not(.visible) .left-column,
+.two-column:not(.visible) .right-column {
+  -webkit-transition: padding-bottom 150ms, padding-top 150ms;
+  padding-bottom: 0;
+  padding-top: 0;
+}
+
 .two-column:not(.visible) select {
   border-top-width: 0;
   margin-top: 0;
   padding-top: 0;
 }
 
 p {
   -webkit-line-box-contain: block;
   margin: 0;
   margin-bottom: 10px;
@@ skipping 61 matching lines @@
 span.hint.closing {
   -webkit-transition: margin 150ms, height 150ms, opacity 150ms;
   background: transparent;
   height: 0 !important;
   margin: 0;
   opacity: 0;
 }
 
 .collapsible {
   height: 0;
+  position: relative;
 }
 
 .collapsible.visible {
   -webkit-animation-duration: 200ms;
   -webkit-animation-fill-mode: forwards;
   height: auto;
 }
 
 .collapsible.closing {
   -webkit-transition: margin 150ms, height 150ms, opacity 150ms;
   height: 0 !important;
   opacity: 0;
   overflow: hidden;
 }
 
+.collapsible.closing > * {
+  position: absolute;
+}
+
 select {
   width: 100%;
 }
 
 label {
   -webkit-user-select: none;
 }
 
 .hidden-section {
   background: white;
@@ skipping 97 matching lines @@
 :enabled:focus:-webkit-any(input[type='checkbox'],
                            input[type='radio'],
                            button):not(.link-button) {
   /* Cancel border-color for :focus specified in widgets.css. */
   border-color: rgba(0,0,0,0.25);
 }
 
 html:not(.focus-outline-visible) button:focus.link-button {
   outline: none;
 }