Support nested matchers in deep equality matching.

pkg/unittest/test/pretty_print_test.dart

Index: pkg/unittest/test/pretty_print_test.dart
diff --git a/pkg/unittest/test/pretty_print_test.dart b/pkg/unittest/test/pretty_print_test.dart
index a0608ac0f9cafa1f248f8dd24e12fef3936584b8..826c345187835125ed807af2ec34150d7bce95f4 100644
--- a/pkg/unittest/test/pretty_print_test.dart
+++ b/pkg/unittest/test/pretty_print_test.dart
@@ -48,6 +48,11 @@ void main() {
           "]"));
     });
 
+    test('containing a matcher', () {
+      expect(prettyPrint(['foo', endsWith('qux')]),
+          equals("['foo', <a string ending with 'qux'>]"));
+    });
+
     test("that's under maxLineLength", () {
       expect(prettyPrint([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], maxLineLength: 30),
           equals("[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"));
@@ -138,6 +143,16 @@ void main() {
           "}"));
     });
 
+    test('containing a matcher key', () {
+      expect(prettyPrint({endsWith('bar'): 'qux'}),
+          equals("{<a string ending with 'bar'>: 'qux'}"));
+    });
+
+    test('containing a matcher value', () {
+      expect(prettyPrint({'foo': endsWith('qux')}),
+          equals("{'foo': <a string ending with 'qux'>}"));
+    });
+
     test("that's under maxLineLength", () {
       expect(prettyPrint({'0': 1, '2': 3, '4': 5, '6': 7}, maxLineLength: 32),
           equals("{'0': 1, '2': 3, '4': 5, '6': 7}"));