Vertical divider (#22641)

* Vertical divider bug fix and additional cleaning.

packages/flutter/lib/src/material/divider.dart

@@ -170,49 +170,17 @@ class VerticalDivider extends StatelessWidget {
   /// ```
   final Color color;
 
-  /// Computes the [BorderSide] that represents a divider of the specified
-  /// color, or, if there is no specified color, of the default
-  /// [ThemeData.dividerColor] specified in the ambient [Theme].
-  ///
-  /// The `width` argument can be used to override the default width of the
-  /// divider border, which is usually 0.0 (a hairline border).
-  ///
-  /// ## Sample code
-  ///
-  /// This example uses this method to create a box that has a divider above and
-  /// below it. This is sometimes useful with lists, for instance, to separate a
-  /// scrollable section from the rest of the interface.
-  ///
-  /// ```dart
-  /// DecoratedBox(
-  ///   decoration: BoxDecoration(
-  ///     border: Border(
-  ///       top: Divider.createBorderSide(context),
-  ///       bottom: Divider.createBorderSide(context),
-  ///     ),
-  ///   ),
-  ///   // child: ...
-  /// )
-  /// ```
-  static BorderSide createBorderSide(BuildContext context, { Color color, double width = 0.0 }) {
-    assert(width != null);
-    return BorderSide(
-      color: color ?? Theme.of(context).dividerColor,
-      width: width,
-    );
-  }
-
   @override
   Widget build(BuildContext context) {
     return SizedBox(
       width: width,
       child: Center(
         child: Container(
-          height: 0.0,
+          width: 0.0,
           margin: EdgeInsetsDirectional.only(start: indent),
           decoration: BoxDecoration(
             border: Border(
-              left: createBorderSide(context, color: color),
+              left: Divider.createBorderSide(context, color: color),
             ),
           ),
         ),

packages/flutter/test/material/divider_test.dart

@@ -35,4 +35,28 @@ void main() {
     expect(box.size.width, 16.0);
     expect(find.byType(VerticalDivider), paints..path(strokeWidth: 0.0));
   });
+
+  testWidgets('Vertical Divider Test 2', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Container(
+            height: 24.0,
+            child: Row(
+              children: const <Widget>[
+                Text('Hey.'),
+                VerticalDivider(),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+    final RenderBox box = tester.firstRenderObject(find.byType(VerticalDivider));
+    final RenderBox containerBox = tester.firstRenderObject(find.byType(Container).last);
+
+    expect(box.size.width, 16.0);
+    expect(containerBox.size.height, 600.0);
+    expect(find.byType(VerticalDivider), paints..path(strokeWidth: 0.0));
+  });
 }