[Android] Add support for standalone PDFium gn build on Android.

core/fxge/android/fx_android_font.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fxcrt/include/fx_system.h"
 
 #if _FX_OS_ == _FX_ANDROID_
 
 #include "core/fxge/android/fpf_skiafont.h"
 #include "core/fxge/android/fpf_skiafontmgr.h"
 #include "core/fxge/android/fx_android_font.h"
 
 CFX_AndroidFontInfo::CFX_AndroidFontInfo() : m_pFontMgr(nullptr) {}
+CFX_AndroidFontInfo::~CFX_AndroidFontInfo() {}
 FX_BOOL CFX_AndroidFontInfo::Init(CFPF_SkiaFontMgr* pFontMgr) {
   if (!pFontMgr)
     return FALSE;
 
   pFontMgr->LoadSystemFonts();
   m_pFontMgr = pFontMgr;
   return TRUE;
 }
 
 FX_BOOL CFX_AndroidFontInfo::EnumFontList(CFX_FontMapper* pMapper) {
@@ skipping 58 matching lines @@
     return;
 
   static_cast<CFPF_SkiaFont*>(hFont)->Release();
 }
 
 void* CFX_AndroidFontInfo::RetainFont(void* hFont) {
   return nullptr;
 }
 
 #endif  // _FX_OS_ == _FX_ANDROID_