Fix bug in setting directories for tests.

make_canonical_dir_path only worked if the provided directory
did not end with a slash. Remove this function, and call
SkPathJoin instead. Update the documentation to acknowledge
that this is an acceptable use of SkPathJoin, and update its
test.

R=epoger@google.com

Review URL: https://codereview.chromium.org/16098011

git-svn-id: http://skia.googlecode.com/svn/trunk@9458 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/OSPathTest.cpp b/tests/OSPathTest.cpp
index 96ff8a7..5ae32eb 100644
--- a/tests/OSPathTest.cpp
+++ b/tests/OSPathTest.cpp
@@ -59,6 +59,12 @@
     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);
@@ -71,6 +77,11 @@
     // 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"