PDF Viewer update: Update sidenav animations duration and timing.

Fixed: 1114268
Change-Id: I9e9c81e53696ff6436c2ce7999067cd213a40191
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2366673
Auto-Submit: dpapad <dpapad@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Reviewed-by: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800208}

chrome/browser/resources/pdf/pdf_viewer.html

@@ -15,12 +15,13 @@
 
   #sidenav-container {
     overflow: hidden;
-    transition: width 250ms ease-out, visibility 250ms;
+    transition: width 250ms cubic-bezier(.6, 0, 0, 1), visibility 250ms;
     visibility: visible;
     width: var(--viewer-pdf-sidenav-width);
   }
 
   #sidenav-container[closed] {
+    transition: width 200ms cubic-bezier(.6, 0, 0, 1), visibility 200ms;
     visibility: hidden;
     width: 0;
   }