Sync lightbox AppBar and BottomAppBar animation

Author: onli

lib/widgets/lightbox.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 import 'package:intl/intl.dart';
 
@@ -132,6 +133,8 @@ class _LightboxPageState extends State<LightboxPage> {
     final appBarBackgroundColor = Colors.grey.shade900.withOpacity(0.87);
     const appBarForegroundColor = Colors.white;
 
+    timeDilation = 20;
+
     // TODO(#45): Format with e.g. "Yesterday at 4:47 PM"
     final timestampText = DateFormat
       .yMMMd(/* TODO(i18n): Pass selected language here, I think? */)
@@ -143,14 +146,15 @@ class _LightboxPageState extends State<LightboxPage> {
       child: AnimatedContainer(
         duration: const Duration(milliseconds: 100),
         curve: Curves.easeIn,
-        height: _headerFooterVisible ? AppBar.preferredHeightFor(context, 
-                                                                  MediaQuery.of(context).size) 
+        height: _headerFooterVisible ? AppBar.preferredHeightFor(
+                                        context, 
+                                        Size(0, MediaQuery.of(context).padding.top + kToolbarHeight)
+                                      ) 
                                       : 0,
         child: AppBar(
           centerTitle: false,
           foregroundColor: appBarForegroundColor,
           backgroundColor: appBarBackgroundColor,
-
           // TODO(#41): Show message author's avatar
           title: RichText(
             text: TextSpan(children: [