Add Pepper TrueType font API call to enumerate fonts in a given family.

ppapi/thunk/ppb_truetype_font_singleton_api.h

Index: ppapi/thunk/ppb_truetype_font_singleton_api.h
diff --git a/ppapi/thunk/ppb_truetype_font_singleton_api.h b/ppapi/thunk/ppb_truetype_font_singleton_api.h
index 514bab1ab6bd09ea5fc8575e29080b1d41c1f487..97c727dc2bb89000bae545bbdfd75d475644a805 100644
--- a/ppapi/thunk/ppb_truetype_font_singleton_api.h
+++ b/ppapi/thunk/ppb_truetype_font_singleton_api.h
@@ -24,6 +24,12 @@ class PPB_TrueTypeFont_Singleton_API {
       const PP_ArrayOutput& output,
       const scoped_refptr<TrackedCallback>& callback) = 0;
 
+  virtual int32_t GetFontsInFamily(
+      PP_Instance instance,
+      PP_Var family,
+      const PP_ArrayOutput& output,
+      const scoped_refptr<TrackedCallback>& callback) = 0;
+
   static const SingletonResourceID kSingletonResourceID =
       TRUETYPE_FONT_SINGLETON_ID;
 };