Move CFX_Font definition to its own file

BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build_overrides/v8.gni")
 import("//testing/test.gni")
 import("pdfium.gni")
 
 config("pdfium_common_config") {
   cflags = []
@@ skipping 750 matching lines @@
     "core/fxge/fontdata/chromefontdata/FoxitSerifMM.cpp",
     "core/fxge/fontdata/chromefontdata/FoxitSymbol.cpp",
     "core/fxge/fontdata/chromefontdata/chromefontdata.h",
     "core/fxge/freetype/fx_freetype.cpp",
     "core/fxge/ge/cfx_autofontcache.cpp",
     "core/fxge/ge/cfx_cliprgn.cpp",
     "core/fxge/ge/cfx_cliprgn.h",
     "core/fxge/ge/cfx_facecache.cpp",
     "core/fxge/ge/cfx_folderfontinfo.cpp",
     "core/fxge/ge/cfx_folderfontinfo.h",
+    "core/fxge/ge/cfx_font.cpp",
     "core/fxge/ge/cfx_fontcache.cpp",
     "core/fxge/ge/cfx_fontmapper.cpp",
     "core/fxge/ge/cfx_fontmgr.cpp",
     "core/fxge/ge/cfx_gemodule.cpp",
     "core/fxge/ge/cfx_graphstatedata.cpp",
     "core/fxge/ge/cfx_pathdata.cpp",
     "core/fxge/ge/cfx_renderdevice.cpp",
     "core/fxge/ge/cfx_substfont.cpp",
     "core/fxge/ge/cfx_unicodeencoding.cpp",
     "core/fxge/ge/cttfontdesc.cpp",
     "core/fxge/ge/cttfontdesc.h",
-    "core/fxge/ge/fx_ge_font.cpp",
     "core/fxge/ge/fx_ge_fontmap.cpp",
     "core/fxge/ge/fx_ge_linux.cpp",
     "core/fxge/ge/fx_ge_text.cpp",
     "core/fxge/ge/fx_text_int.h",
     "core/fxge/ifx_renderdevicedriver.cpp",
     "core/fxge/include/cfx_autofontcache.h",
     "core/fxge/include/cfx_facecache.h",
     "core/fxge/include/cfx_fontcache.h",
     "core/fxge/include/cfx_fontmapper.h",
     "core/fxge/include/cfx_fontmgr.h",
@@ skipping 923 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }