Remove dependence of fpdfxfa on fpdfdoc.

It isn't required at present in the first place. As a check, putting

#define CORE_FPDFDOC_CPDF_INTERACTIVEFORM_H_

in the top of pdfxfa_widgethandler.cpp to force exclusion of the one
dependent header still results in a clean compilation (on linux).

Change-Id: I7b644d4f6d438ed4e1e2e049fe6d487063db6993
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/59210
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

fpdfsdk/fpdfxfa/BUILD.gn

diff --git a/fpdfsdk/fpdfxfa/BUILD.gn b/fpdfsdk/fpdfxfa/BUILD.gn
index 4e80ffe..9d9788d 100644
--- a/fpdfsdk/fpdfxfa/BUILD.gn
+++ b/fpdfsdk/fpdfxfa/BUILD.gn
@@ -26,7 +26,6 @@
     "../../core/fpdfapi/page",
     "../../core/fpdfapi/parser",
     "../../core/fpdfapi/render",
-    "../../core/fpdfdoc",
     "../../core/fxcrt",
     "../../fxjs",
     "../../xfa/fwl",

fpdfsdk/fpdfxfa/cpdfxfa_widgethandler.cpp

diff --git a/fpdfsdk/fpdfxfa/cpdfxfa_widgethandler.cpp b/fpdfsdk/fpdfxfa/cpdfxfa_widgethandler.cpp
index 952079c..5c5b9e9 100644
--- a/fpdfsdk/fpdfxfa/cpdfxfa_widgethandler.cpp
+++ b/fpdfsdk/fpdfxfa/cpdfxfa_widgethandler.cpp
@@ -6,7 +6,6 @@
 
 #include "fpdfsdk/fpdfxfa/cpdfxfa_widgethandler.h"
 
-#include "core/fpdfdoc/cpdf_interactiveform.h"
 #include "fpdfsdk/cpdfsdk_annot.h"
 #include "fpdfsdk/cpdfsdk_formfillenvironment.h"
 #include "fpdfsdk/cpdfsdk_interactiveform.h"