Reverts "sliverGridDelegate mainAxisExtent add assert (#148470)" (#149224)

Reverts: flutter/flutter#148470
Initiated by: eyebrowsoffire
Reason for reverting: Unit test failures closing the tree.
Original PR Author: hello-coder-xu

Reviewed By: {QuncCccccc, Piinks}

This change reverts the following previous change:
* sliverGridDelegate mainAxisExtent add assert,Avoid incorrect use *

Fixes flutter/flutter#138871

Author: auto-submit[bot]

packages/flutter/lib/src/rendering/sliver_grid.dart

@@ -348,8 +348,7 @@ class SliverGridDelegateWithFixedCrossAxisCount extends SliverGridDelegate {
   }) : assert(crossAxisCount > 0),
        assert(mainAxisSpacing >= 0),
        assert(crossAxisSpacing >= 0),
-       assert(childAspectRatio > 0),
-       assert(mainAxisExtent == null || mainAxisExtent >= 0);
+       assert(childAspectRatio > 0);
 
   /// The number of children in the cross axis.
   final int crossAxisCount;
@@ -447,8 +446,7 @@ class SliverGridDelegateWithMaxCrossAxisExtent extends SliverGridDelegate {
   }) : assert(maxCrossAxisExtent > 0),
        assert(mainAxisSpacing >= 0),
        assert(crossAxisSpacing >= 0),
-       assert(childAspectRatio > 0),
-       assert(mainAxisExtent == null || mainAxisExtent >= 0);
+       assert(childAspectRatio > 0);
 
   /// The maximum extent of tiles in the cross axis.
   ///

packages/flutter/test/widgets/grid_view_test.dart

@@ -898,53 +898,4 @@ void main() {
     expect(controller.position.maxScrollExtent, 472.0);
     expect(controller.position.pixels, 472.0);
   });
-
-  testWidgets('SliverGridDelegate mainAxisExtent add assert', (WidgetTester tester) async {
-    Widget buildGridView(SliverGridDelegate delegate) {
-      return Directionality(
-        textDirection: TextDirection.ltr,
-        child: GridView.builder(
-          gridDelegate: delegate,
-          itemBuilder: (BuildContext context, int index) {
-            return Container(
-              height: 50,
-              alignment: Alignment.center,
-              child: Text('$index'),
-            );
-          },
-          itemCount: 50,
-        ),
-      );
-    }
-
-    expect(
-      () => tester.pumpWidget(buildGridView(SliverGridDelegateWithFixedCrossAxisCount(
-        crossAxisCount: 3,
-        mainAxisSpacing: 8,
-        crossAxisSpacing: 8,
-        mainAxisExtent: -100,
-      ))),
-      throwsA(isAssertionError.having(
-        (AssertionError e) => e.toString(),
-        '.toString()',
-        contains("'mainAxisExtent == null || mainAxisExtent >= 0': is not true."),
-      )),
-    );
-
-    expect(
-      () => tester.pumpWidget(buildGridView(SliverGridDelegateWithMaxCrossAxisExtent(
-        maxCrossAxisExtent: 100,
-        mainAxisSpacing: 8,
-        crossAxisSpacing: 8,
-        mainAxisExtent: -100,
-      ))),
-      throwsA(isAssertionError.having(
-        (AssertionError e) => e.toString(),
-        '.toString()',
-        contains("'mainAxisExtent == null || mainAxisExtent >= 0': is not true."),
-      )),
-    );
-  });
-
-
 }