Fix outline button solid path when BorderSize.width is used (#51581)

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

@@ -561,7 +561,7 @@ class _OutlineBorder extends ShapeBorder implements MaterialStateProperty<ShapeB
       case BorderStyle.none:
         break;
       case BorderStyle.solid:
-        canvas.drawPath(shape.getOuterPath(rect, textDirection: textDirection), side.toPaint());
+        canvas.drawPath(shape.getOuterPath(rect.deflate(side.width / 2.0), textDirection: textDirection), side.toPaint());
     }
   }
 

packages/flutter/test/material/outline_button_test.dart

@@ -867,6 +867,39 @@ void main() {
     );
   });
 
+  testWidgets('OutlineButton uses borderSide width to paint', (WidgetTester tester) async {
+    final GlobalKey buttonKey = GlobalKey();
+    const double thickness = 12.5;
+    await tester.pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: Material(
+          child: Align(
+            alignment: Alignment.topLeft,
+            child: OutlineButton(
+              key: buttonKey,
+              borderSide: const BorderSide(
+                  color: Colors.black12,
+                  width: thickness),
+              onPressed: () {},
+              child: const SizedBox(
+                  width: 120,
+                  height: 50,
+                  child: Text('ABC'),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final Finder outlineButton = find.byType(OutlineButton);
+    expect(outlineButton, paints..path(
+      includes: const <Offset>[Offset(60, thickness / 2.0)],
+      excludes: const <Offset>[Offset(60, thickness / 3.0)],
+    ));
+  });
+
   testWidgets('OutlineButton contributes semantics', (WidgetTester tester) async {
     final SemanticsTester semantics = SemanticsTester(tester);
     await tester.pumpWidget(

packages/flutter/test/rendering/mock_canvas.dart

@@ -1163,13 +1163,15 @@ class _PathPaintPredicate extends _DrawCommandPaintPredicate {
     if (includes != null) {
       for (final Offset offset in includes) {
         if (!pathArgument.contains(offset))
-          throw 'It called $methodName with a path that unexpectedly did not contain $offset.';
+          throw 'It called $methodName with a path that unexpectedly did not '
+              'contain $offset. Path bounds = ${pathArgument.getBounds()}';
       }
     }
     if (excludes != null) {
       for (final Offset offset in excludes) {
         if (pathArgument.contains(offset))
-          throw 'It called $methodName with a path that unexpectedly contained $offset.';
+          throw 'It called $methodName with a path that unexpectedly '
+              'contained $offset. . Path bounds = ${pathArgument.getBounds()}';
       }
     }
   }