Update scaffold test bottom bar height (#13429)

This patch contains no framework changes.

This change adjusts a test bottom navigation bar height to be greater
than the media bottom padding.

This change is pre-factoring to clarify diffs in an upcoming change that
will expose bottom padding to the bottom navigation bar in order to
allow it to visually adapt its appearance in the presence of bottom
padding such as thatexposed for the iPhone X home screen indicator.
Since the bottom padding was previously greater than the height of the
bottom navigation bar, the height of insideBottomNavigation bar was
driven to 0 when padding is exposed.

packages/flutter/test/material/scaffold_test.dart

@@ -631,7 +631,7 @@ void main() {
             ),
             bottomNavigationBar: new SizedBox(
               key: bottomNavigationBar,
-              height: 55.0,
+              height: 85.0,
               child: new SafeArea(
                 child: new Placeholder(key: insideBottomNavigationBar),
               ),
@@ -646,17 +646,17 @@ void main() {
     await tester.pump(const Duration(seconds: 1));
 
     expect(tester.getRect(find.byKey(appBar)), new Rect.fromLTRB(0.0, 0.0, 800.0, 43.0));
-    expect(tester.getRect(find.byKey(body)), new Rect.fromLTRB(0.0, 43.0, 800.0, 368.0));
-    expect(tester.getRect(find.byKey(floatingActionButton)), new Rect.fromLTRB(36.0, 275.0, 113.0, 352.0));
-    expect(tester.getRect(find.byKey(persistentFooterButton)), new Rect.fromLTRB(28.0, 377.0, 128.0, 467.0));
+    expect(tester.getRect(find.byKey(body)), new Rect.fromLTRB(0.0, 43.0, 800.0, 338.0));
+    expect(tester.getRect(find.byKey(floatingActionButton)), new Rect.fromLTRB(36.0, 245.0, 113.0, 322.0));
+    expect(tester.getRect(find.byKey(persistentFooterButton)), new Rect.fromLTRB(28.0, 347.0, 128.0, 437.0));
     expect(tester.getRect(find.byKey(drawer)), new Rect.fromLTRB(596.0, 0.0, 800.0, 600.0));
-    expect(tester.getRect(find.byKey(bottomNavigationBar)), new Rect.fromLTRB(0.0, 475.0, 800.0, 530.0));
+    expect(tester.getRect(find.byKey(bottomNavigationBar)), new Rect.fromLTRB(0.0, 445.0, 800.0, 530.0));
     expect(tester.getRect(find.byKey(insideAppBar)), new Rect.fromLTRB(20.0, 30.0, 750.0, 43.0));
-    expect(tester.getRect(find.byKey(insideBody)), new Rect.fromLTRB(20.0, 43.0, 750.0, 368.0));
-    expect(tester.getRect(find.byKey(insideFloatingActionButton)), new Rect.fromLTRB(36.0, 275.0, 113.0, 352.0));
-    expect(tester.getRect(find.byKey(insidePersistentFooterButton)), new Rect.fromLTRB(28.0, 377.0, 128.0, 467.0));
+    expect(tester.getRect(find.byKey(insideBody)), new Rect.fromLTRB(20.0, 43.0, 750.0, 338.0));
+    expect(tester.getRect(find.byKey(insideFloatingActionButton)), new Rect.fromLTRB(36.0, 245.0, 113.0, 322.0));
+    expect(tester.getRect(find.byKey(insidePersistentFooterButton)), new Rect.fromLTRB(28.0, 347.0, 128.0, 437.0));
     expect(tester.getRect(find.byKey(insideDrawer)), new Rect.fromLTRB(596.0, 30.0, 750.0, 530.0));
-    expect(tester.getRect(find.byKey(insideBottomNavigationBar)), new Rect.fromLTRB(20.0, 475.0, 750.0, 530.0));
+    expect(tester.getRect(find.byKey(insideBottomNavigationBar)), new Rect.fromLTRB(20.0, 445.0, 750.0, 530.0));
   });
 
   testWidgets('Simultaneous drawers on either side', (WidgetTester tester) async {