Allows a Typeface object to be added to ReactFontManager

Summary:
Currently on Android, React Native can only accept font resource IDs which it internally converts into Typeface objects. This change allows ReactFontManager to be passed a Typeface at runtime to enable e.g. downloading fonts on demand.

Changelog:
[Android][Added] - Ability to pass a Typeface object to ReactFontManager in addition to a font resource ID

Reviewed By: makovkastar

Differential Revision: D36138123

fbshipit-source-id: b314e8c7fc28174b5caa017076b6eb3d4f6dbaa8

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactFontManager.java

@@ -110,6 +110,16 @@ public void addCustomFont(Context context, String fontFamily, int fontId) {
     }
   }
 
+  /**
+   * Equivalent method to {@see addCustomFont(Context, String, int)} which accepts a Typeface
+   * object.
+   */
+  public void addCustomFont(String fontFamily, @Nullable Typeface font) {
+    if (font != null) {
+      mCustomTypefaceCache.put(fontFamily, font);
+    }
+  }
+
   /**
    * Add additional font family, or replace the exist one in the font memory cache.
    *