Merge CPDFXFA_App into CPDFXFA_Document.

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 1036 matching lines @@
         "fxjs/cfxjse_value.h",
         "fxjs/fxjse.h",
       ]
     }
   }
 }
 
 if (pdf_enable_xfa) {
   static_library("fpdfxfa") {
     sources = [
-      "fpdfsdk/fpdfxfa/cpdfxfa_app.cpp",
-      "fpdfsdk/fpdfxfa/cpdfxfa_app.h",
       "fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp",
       "fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.h",
       "fpdfsdk/fpdfxfa/cpdfxfa_document.cpp",
       "fpdfsdk/fpdfxfa/cpdfxfa_document.h",
       "fpdfsdk/fpdfxfa/cpdfxfa_page.cpp",
       "fpdfsdk/fpdfxfa/cpdfxfa_page.h",
       "fpdfsdk/fpdfxfa/cxfa_fwladaptertimermgr.cpp",
       "fpdfsdk/fpdfxfa/cxfa_fwladaptertimermgr.h",
     ]
     deps = [
@@ skipping 686 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }