Refactor SkFontHost_linux into SkFontMgr_custom.

src/ports/SkFontMgr_custom_directory_factory.cpp

Index: src/ports/SkFontMgr_custom_directory_factory.cpp
diff --git a/src/ports/SkFontMgr_custom_directory_factory.cpp b/src/ports/SkFontMgr_custom_directory_factory.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..0ca6f4b3b4b6968232437381278f13239ab3a3c9
--- /dev/null
+++ b/src/ports/SkFontMgr_custom_directory_factory.cpp
@@ -0,0 +1,17 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkFontMgr.h"
+#include "SkFontMgr_custom.h"
+
+#ifndef SK_FONT_FILE_PREFIX
+#    define SK_FONT_FILE_PREFIX "/usr/share/fonts/"
+#endif
+
+SkFontMgr* SkFontMgr::Factory() {
+    return SkFontMgr_New_Custom_Directory(SK_FONT_FILE_PREFIX);
+}