Add path utils, plus a test for it.

src/utils/SkOSPathUtils.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 "SkOSFile.h"
+#include "SkOSPathUtils.h"
+#include "SkString.h"
+
+SkString SkPathJoin(const char *rootPath, const char *relativePath) {
+    SkString result(rootPath);
+    if (!result.endsWith(SkPATH_SEPARATOR)) {
+        result.appendUnichar(SkPATH_SEPARATOR);
+    }
+    result.append(relativePath);
+    return result;
+}
+
+const char* SkBasename(const char* fullPath) {
+    const char* filename = strrchr(fullPath, SkPATH_SEPARATOR);
+    if (NULL == filename || *++filename == '\0') {
+        filename = fullPath;
+    }
+    return filename;
+}