Stop using unittest in point_test and rectangle_test.

pkg/dev_compiler/tool/sdk_expected_errors.txt

Index: pkg/dev_compiler/tool/sdk_expected_errors.txt
diff --git a/pkg/dev_compiler/tool/sdk_expected_errors.txt b/pkg/dev_compiler/tool/sdk_expected_errors.txt
index 6ab53ca3df1b50234d86c1e719ab63f5714154ba..7be6c6564195710c669ecb4669d68b58c987e2c9 100644
--- a/pkg/dev_compiler/tool/sdk_expected_errors.txt
+++ b/pkg/dev_compiler/tool/sdk_expected_errors.txt
@@ -119,9 +119,9 @@
 [warning] Unsound implicit cast from dynamic to Rectangle<num> (dart:html, line 37634, col 14)
 [warning] Unsound implicit cast from (T) → void to (Event) → dynamic (dart:html, line 40090, col 67)
 [warning] Unsound implicit cast from (T) → void to (Event) → dynamic (dart:html, line 40112, col 45)
-[warning] Unsound implicit cast from num to T (dart:math/rectangle.dart, line 151, col 22)
-[warning] Unsound implicit cast from num to T (dart:math/rectangle.dart, line 152, col 23)
-[warning] Unsound implicit cast from num to T (dart:math/rectangle.dart, line 275, col 10)
+[warning] Unsound implicit cast from num to T (dart:math/rectangle.dart, line 158, col 22)
+[warning] Unsound implicit cast from num to T (dart:math/rectangle.dart, line 159, col 23)
+[warning] Unsound implicit cast from num to T (dart:math/rectangle.dart, line 282, col 10)
 [warning] The final variables 'href' and 'target' must be initialized (dart:svg, line 60, col 3)
 [warning] The final variables 'requiredExtensions', 'requiredFeatures' and '2' more must be initialized (dart:svg, line 489, col 3)
 [warning] The final variables 'cx', 'cy' and '1' more must be initialized (dart:svg, line 562, col 3)