Enforce pure virtual behavior for onMatchFamilyStyleCharacter

include/ports/SkFontMgr.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkFontMgr_DEFINED
 #define SkFontMgr_DEFINED
 
@@ skipping 103 matching lines @@
 protected:
     virtual int onCountFamilies() const = 0;
     virtual void onGetFamilyName(int index, SkString* familyName) const = 0;
     virtual SkFontStyleSet* onCreateStyleSet(int index)const  = 0;
 
     /** May return NULL if the name is not found. */
     virtual SkFontStyleSet* onMatchFamily(const char familyName[]) const = 0;
 
     virtual SkTypeface* onMatchFamilyStyle(const char familyName[],
                                            const SkFontStyle&) const = 0;
-    // TODO: pure virtual, implement on all impls.
     virtual SkTypeface* onMatchFamilyStyleCharacter(const char familyName[], const SkFontStyle&,
                                                     const char* bcp47[], int bcp47Count,
-                                                    SkUnichar character) const
-    { return NULL; }
+                                                    SkUnichar character) const = 0;
     virtual SkTypeface* onMatchFaceStyle(const SkTypeface*,
                                          const SkFontStyle&) const = 0;
 
     virtual SkTypeface* onCreateFromData(SkData*, int ttcIndex) const = 0;
     virtual SkTypeface* onCreateFromStream(SkStream*, int ttcIndex) const = 0;
     virtual SkTypeface* onCreateFromFile(const char path[], int ttcIndex) const = 0;
 
     virtual SkTypeface* onLegacyCreateTypeface(const char familyName[],
                                                unsigned styleBits) const = 0;
 private:
     static SkFontMgr* Factory();    // implemented by porting layer
     friend SkFontMgr* sk_fontmgr_create_default();
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif