bring pdfium file in sync with chrome, fix mac build

skia/skia_gn_files.gypi

 # This file is read into the GN build.
 
 # Files are relative to third_party/skia.
 {
   'skia_library_sources': [
     '<(skia_src_path)/ports/SkImageGenerator_none.cpp',
 
     '<(skia_src_path)/fonts/SkFontMgr_indirect.cpp',
     '<(skia_src_path)/fonts/SkRemotableFontMgr.cpp',
     '<(skia_src_path)/ports/SkFontHost_FreeType_common.cpp',
     '<(skia_src_path)/ports/SkFontHost_FreeType.cpp',
-    '<(skia_src_path)/ports/SkFontHost_mac.cpp',
     '<(skia_src_path)/ports/SkFontHost_win.cpp',
     '<(skia_src_path)/ports/SkFontMgr_android.cpp',
     '<(skia_src_path)/ports/SkFontMgr_android_factory.cpp',
     '<(skia_src_path)/ports/SkFontMgr_android_parser.cpp',
     '<(skia_src_path)/ports/SkGlobalInitialization_default.cpp',
     '<(skia_src_path)/ports/SkImageEncoder_none.cpp',
     '<(skia_src_path)/ports/SkOSFile_posix.cpp',
     '<(skia_src_path)/ports/SkOSFile_stdio.cpp',
     '<(skia_src_path)/ports/SkOSFile_win.cpp',
     '<(skia_src_path)/ports/SkRemotableFontMgr_win_dw.cpp',
@@ skipping 12 matching lines @@
     #testing
     '<(skia_src_path)/fonts/SkGScalerContext.cpp',
 
     #pdfium
     '<(skia_src_path)/ports/SkDiscardableMemory_none.cpp',
     '<(skia_src_path)/ports/SkFontMgr_custom.cpp',
     '<(skia_src_path)/ports/SkFontMgr_custom_empty_factory.cpp',
     '<(skia_src_path)/ports/SkMemory_malloc.cpp',
   ],
 }