Add factory for Android font manager.

include/ports/SkFontMgr_android.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkFontMgr_android_DEFINED
+#define SkFontMgr_android_DEFINED
+
+#include "SkTypes.h"
+
+class SkFontMgr;
+
+struct SkFontMgr_Android_CustomFonts {
+    /** When specifying custom fonts, indicates how to use system fonts. */
+    enum SystemFontUse {
+        kOnlyCustom, /** Use only custom fonts. NDK compliant. */
+        kPreferCustom, /** Use custom fonts before system fonts. */
+        kPreferSystem /** Use system fonts before custom fonts. */
+    };
+    /** Whether or not to use system fonts. */
+    SystemFontUse fSystemFontUse;
+
+    /** Base path to resolve relative font file names. If a directory, should end with '/'. */
+    const char* fBasePath;
+
+    /** Optional custom configuration file to use. */
+    const char* fFontsXml;
+
+    /** Optional custom configuration file for fonts which provide fallback.
+     *  In the new style (version > 21) fontsXml format is used, this should be NULL.
+     */
+    const char* fFallbackFontsXml;
+};
+
+/** Create a font manager for Android. If 'custom' is NULL, use only system fonts. */
+SK_API SkFontMgr* SkFontMgr_New_Android(const SkFontMgr_Android_CustomFonts* custom);
+
+#endif // SkFontMgr_android_DEFINED