Fix clang_use_chrome_plugin for Mac and Skia builds

core/fxge/apple/apple_int.h

 // 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
 
 #ifndef CORE_FXGE_APPLE_APPLE_INT_H_
 #define CORE_FXGE_APPLE_APPLE_INT_H_
 
 #include "core/fxcrt/include/fx_system.h"
@@ skipping 116 matching lines @@
                         int dest_height,
                         const FX_RECT* pClipRect,
                         uint32_t flags,
                         int blend_type) override;
   FX_BOOL StartDIBits(const CFX_DIBSource* pBitmap,
                       int bitmap_alpha,
                       uint32_t color,
                       const CFX_Matrix* pMatrix,
                       uint32_t flags,
                       void*& handle,
-                      int blend_type) override {
-    return FALSE;
-  }
+                      int blend_type) override;
   FX_BOOL DrawDeviceText(int nChars,
                          const FXTEXT_CHARPOS* pCharPos,
                          CFX_Font* pFont,
                          CFX_FontCache* pCache,
                          const CFX_Matrix* pObject2Device,
                          FX_FLOAT font_size,
                          uint32_t color) override;
   void ClearDriver() override;
 
  protected:
@@ skipping 32 matching lines @@
   int32_t m_vertSize;
 };
 
 uint32_t FX_GetHashCode(const FX_CHAR* pStr);
 uint32_t FX_IOSGetMatchFamilyNameHashcode(const FX_CHAR* pFontName);
 uint32_t FX_IOSGetFamilyNamesCount();
 const FX_CHAR* FX_IOSGetFamilyName(uint32_t uIndex);
 #endif
 
 #endif  // CORE_FXGE_APPLE_APPLE_INT_H_