RenderWrap.performLayout should take spacing into consideration (#15256)

* RenderWrap.performLayout takes should take spacing into consideration when deciding to move to next row/axis

* fix spacing in text

* remove dart:developer import

* remove extra line

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

@@ -608,7 +608,7 @@ class RenderWrap extends RenderBox with ContainerRenderObjectMixin<RenderBox, Wr
       child.layout(childConstraints, parentUsesSize: true);
       final double childMainAxisExtent = _getMainAxisExtent(child);
       final double childCrossAxisExtent = _getCrossAxisExtent(child);
-      if (runMainAxisExtent + childMainAxisExtent > mainAxisLimit) {
+      if (runMainAxisExtent + childMainAxisExtent + spacing > mainAxisLimit) {
         assert(childCount > 0);
         mainAxisExtent = math.max(mainAxisExtent, runMainAxisExtent);
         crossAxisExtent += runCrossAxisExtent;

packages/flutter/test/widgets/wrap_test.dart

@@ -828,4 +828,27 @@ void main() {
     expect(tester.renderObject<RenderBox>(find.byType(Baseline)).size,
            within<Size>(from: const Size(100.0, 200.0), distance: 0.001));
   });
+
+  testWidgets('Spacing with slight overflow', (WidgetTester tester) async {
+    await tester.pumpWidget(new Wrap(
+      direction: Axis.horizontal,
+      textDirection: TextDirection.ltr,
+      spacing: 10.0,
+      runSpacing: 10.0,
+      children: <Widget>[
+        const SizedBox(width: 200.0, height: 10.0),
+        const SizedBox(width: 200.0, height: 10.0),
+        const SizedBox(width: 200.0, height: 10.0),
+        const SizedBox(width: 171.0, height: 10.0),
+      ],
+    ));
+
+    expect(tester.renderObject<RenderBox>(find.byType(Wrap)).size, equals(const Size(800.0, 600.0)));
+    verify(tester, <Offset>[
+      const Offset(0.0, 0.0),
+      const Offset(210.0, 0.0),
+      const Offset(420.0, 0.0),
+      const Offset(0.0, 20.0)
+    ]);
+  });
 }