Add support for caching font files in the Android SkFontMgr.

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
 
@@ skipping 21 matching lines @@
     /** 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;
+
+    /** Optional custom flag. If set to true the SkFontMgr will acquire all requisite
+     *  system IO resources on initialization.
+     */
+    bool fIsolated;

[bungeman-skia, 2016/02/12 18:59:35]

Question for reed: should this be an enum?

 };
 
 /** 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