Make StateData private

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index b2f16b3ff14f48bc25c6bcefb8abd4ca9561c188..2add64e93d51673b5842098bb5a56031577fe961 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -426,7 +426,6 @@ static_library("fpdfapi") {
     "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",
@@ -465,7 +464,6 @@ static_library("fpdfapi") {
     "core/fpdfapi/fpdf_page/include/cpdf_form.h",
     "core/fpdfapi/fpdf_page/include/cpdf_formobject.h",
     "core/fpdfapi/fpdf_page/include/cpdf_generalstate.h",
-    "core/fpdfapi/fpdf_page/include/cpdf_generalstatedata.h",
     "core/fpdfapi/fpdf_page/include/cpdf_image.h",
     "core/fpdfapi/fpdf_page/include/cpdf_imageobject.h",
     "core/fpdfapi/fpdf_page/include/cpdf_page.h",