Fix bug in setting directories for tests.

tests/OSPathTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkString.h"
 #include "SkOSFile.h"
 #include "Test.h"
@@ skipping 41 matching lines @@
 
 static void test_os_path_utils_tests(skiatest::Reporter* reporter) {
     SkString dir("dir");
     SkString filename("file");
     test_dir_with_file(reporter, dir, filename);
 
     // Now make sure this works with a path separator at the end of dir.
     dir.appendUnichar(SkPATH_SEPARATOR);
     test_dir_with_file(reporter, dir, filename);
 
+    // Test using no filename.
+    test_dir_with_file(reporter, dir, SkString());
+
+    // Testing using no directory.
+    test_dir_with_file(reporter, SkString(), filename);
+
     // Test with a sub directory.
     dir.append("subDir");
     test_dir_with_file(reporter, dir, filename);
 
     // Basename of a directory with a path separator at the end is empty.
     dir.appendUnichar(SkPATH_SEPARATOR);
     SkString baseOfDir = SkOSPath::SkBasename(dir.c_str());
     REPORTER_ASSERT(reporter, baseOfDir.size() == 0);
 
     // Basename of NULL is an empty string.
     SkString empty = SkOSPath::SkBasename(NULL);
     REPORTER_ASSERT(reporter, empty.size() == 0);
+
+    // Test that NULL can be used for the directory and filename.
+    SkString emptyPath = SkOSPath::SkPathJoin(NULL, NULL);
+    REPORTER_ASSERT(reporter, emptyPath.size() == 1);
+    REPORTER_ASSERT(reporter, emptyPath.contains(SkPATH_SEPARATOR));
 }
 
 #include "TestClassDef.h"
 DEFINE_TESTCLASS("OSPath", OSPathTestClass, test_os_path_utils_tests)