Mac: Implement GetFallbackFontFamilies for Harfbuzz

ui/gfx/font_fallback_mac_unittest.cc

Index: ui/gfx/font_fallback_mac_unittest.cc
diff --git a/ui/gfx/font_fallback_mac_unittest.cc b/ui/gfx/font_fallback_mac_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..689ec6d045e4639b50f4fe6c4e9ae6f06eb402aa
--- /dev/null
+++ b/ui/gfx/font_fallback_mac_unittest.cc
@@ -0,0 +1,21 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/gfx/font_fallback.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace gfx {
+
+// A targeted test for GetFallbackFontFamilies on Mac. It uses a system API that
+// only became publicly available in the 10.8 SDK. This test is to ensure it
+// behaves sensibly on all supported OS versions.
+GTEST_TEST(FontFallbackMacTest, GetFallbackFontFamilies) {
+  std::vector<std::string> fallback_families = GetFallbackFontFamilies("Arial");
+  // If there is only one fallback, it means the only fallback is the font
+  // itself.
+  EXPECT_LT(1u, fallback_families.size());
+}
+
+}  // namespace gfx