Make CPDF_GraphState have a CPDF_GraphStateData instead of inheriting

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 411 matching lines @@
     "core/fpdfapi/fpdf_page/cpdf_contentmarkdata.h",
     "core/fpdfapi/fpdf_page/cpdf_contentmarkitem.cpp",
     "core/fpdfapi/fpdf_page/cpdf_contentmarkitem.h",
     "core/fpdfapi/fpdf_page/cpdf_countedobject.h",
     "core/fpdfapi/fpdf_page/cpdf_form.cpp",
     "core/fpdfapi/fpdf_page/cpdf_formobject.cpp",
     "core/fpdfapi/fpdf_page/cpdf_generalstate.cpp",
     "core/fpdfapi/fpdf_page/cpdf_generalstatedata.cpp",
     "core/fpdfapi/fpdf_page/cpdf_graphicstates.cpp",
     "core/fpdfapi/fpdf_page/cpdf_graphicstates.h",
+    "core/fpdfapi/fpdf_page/cpdf_graphstate.cpp",
     "core/fpdfapi/fpdf_page/cpdf_graphstate.h",
     "core/fpdfapi/fpdf_page/cpdf_image.cpp",
     "core/fpdfapi/fpdf_page/cpdf_imageobject.cpp",
     "core/fpdfapi/fpdf_page/cpdf_meshstream.cpp",
     "core/fpdfapi/fpdf_page/cpdf_meshstream.h",
     "core/fpdfapi/fpdf_page/cpdf_page.cpp",
     "core/fpdfapi/fpdf_page/cpdf_pagemodule.cpp",
     "core/fpdfapi/fpdf_page/cpdf_pagemodule.h",
     "core/fpdfapi/fpdf_page/cpdf_pageobject.cpp",
     "core/fpdfapi/fpdf_page/cpdf_pageobjectholder.cpp",
@@ skipping 1267 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }