Optimize paths comparision in source closure sorting.

pkg/analyzer/test/src/summary/incremental_cache_test.dart

Index: pkg/analyzer/test/src/summary/incremental_cache_test.dart
diff --git a/pkg/analyzer/test/src/summary/incremental_cache_test.dart b/pkg/analyzer/test/src/summary/incremental_cache_test.dart
index 695cb51ac3e76f06ff0210ea8bfa6ccb6f9de2e6..3a8cfc5345d5d4ae55b5b961aa37e3d37a6b08d9 100644
--- a/pkg/analyzer/test/src/summary/incremental_cache_test.dart
+++ b/pkg/analyzer/test/src/summary/incremental_cache_test.dart
@@ -14,9 +14,57 @@ import '../abstract_single_unit.dart';
 
 main() {
   groupSep = ' | ';
+  runReflectiveTests(ComparePathsTest);
   runReflectiveTests(IncrementalCacheTest);
 }
 
+@reflectiveTest
+class ComparePathsTest extends AbstractSingleUnitTest {
+  void test_empty() {
+    expect(comparePaths('', ''), 0);
+  }
+
+  void test_equal() {
+    expect(comparePaths('abc', 'abc'), 0);
+  }
+
+  void test_longer_suffixAfter() {
+    expect(comparePaths('aab', 'aa'), 1);
+  }
+
+  void test_longer_suffixBefore() {
+    expect(comparePaths('aaa', 'ab'), -1);
+  }
+
+  void test_longer_suffixSame() {
+    expect(comparePaths('aaa', 'aa'), 1);
+  }
+
+  void test_sameLength_before0() {
+    expect(comparePaths('aaa', 'bbb'), -1);
+  }
+
+  void test_sameLength_before1() {
+    expect(comparePaths('aaa', 'bba'), -1);
+  }
+
+  void test_sameLength_before2() {
+    expect(comparePaths('aaa', 'bba'), -1);
+  }
+
+  void test_shorter_suffixAfter() {
+    expect(comparePaths('ab', 'aaa'), 1);
+  }
+
+  void test_shorter_suffixBefore() {
+    expect(comparePaths('aa', 'aab'), -1);
+  }
+
+  void test_shorter_suffixSame() {
+    expect(comparePaths('aa', 'aaa'), -1);
+  }
+}
+
 /**
  * TODO(scheglov) write more tests for invalidation.
  */