Make some methods const in XFAJSEmbedderTest

This CL addresses the published draft comment from
https://pdfium-review.googlesource.com/c/pdfium/+/5691/

Change-Id: I7a2cd9aa5dbdde18cadb82cbef70f0e8820cc276
Reviewed-on: https://pdfium-review.googlesource.com/42871
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>

testing/embedder_test.h

diff --git a/testing/embedder_test.h b/testing/embedder_test.h
index ef4fe02..6470763 100644
--- a/testing/embedder_test.h
+++ b/testing/embedder_test.h
@@ -81,8 +81,8 @@
     delegate_ = delegate ? delegate : default_delegate_.get();
   }
 
-  FPDF_DOCUMENT document() { return document_; }
-  FPDF_FORMHANDLE form_handle() { return form_handle_; }
+  FPDF_DOCUMENT document() const { return document_; }
+  FPDF_FORMHANDLE form_handle() const { return form_handle_; }
 
   // Create an empty document, and its form fill environment. Returns true
   // on success or false on failure.

testing/xfa_js_embedder_test.cpp

diff --git a/testing/xfa_js_embedder_test.cpp b/testing/xfa_js_embedder_test.cpp
index 97009f3..8d2f64e 100644
--- a/testing/xfa_js_embedder_test.cpp
+++ b/testing/xfa_js_embedder_test.cpp
@@ -43,7 +43,7 @@
   isolate_ = nullptr;
 }
 
-CXFA_Document* XFAJSEmbedderTest::GetXFADocument() {
+CXFA_Document* XFAJSEmbedderTest::GetXFADocument() const {
   auto* pDoc = CPDFDocumentFromFPDFDocument(document());
   if (!pDoc)
     return nullptr;

testing/xfa_js_embedder_test.h

diff --git a/testing/xfa_js_embedder_test.h b/testing/xfa_js_embedder_test.h
index 27dddc3..3534280 100644
--- a/testing/xfa_js_embedder_test.h
+++ b/testing/xfa_js_embedder_test.h
@@ -31,12 +31,12 @@
                                JavaScriptOption javascript_option) override;
 
   v8::Isolate* GetIsolate() const { return isolate_; }
-  CXFA_Document* GetXFADocument();
+  CXFA_Document* GetXFADocument() const;
 
   bool Execute(const ByteStringView& input);
   bool ExecuteSilenceFailure(const ByteStringView& input);
 
-  CFXJSE_Engine* GetScriptContext() { return script_context_; }
+  CFXJSE_Engine* GetScriptContext() const { return script_context_; }
   CFXJSE_Value* GetValue() const { return value_.get(); }
 
  private: