Fixup page removal for XFA documents.

fpdfsdk/fpdfdoc_embeddertest.cpp

Index: fpdfsdk/fpdfdoc_embeddertest.cpp
diff --git a/fpdfsdk/fpdfdoc_embeddertest.cpp b/fpdfsdk/fpdfdoc_embeddertest.cpp
index 855235858b2bada749bba8cfcf3357b9ad264072..2450b6aea61cc829a3d59e6f71fd40adee61ff6e 100644
--- a/fpdfsdk/fpdfdoc_embeddertest.cpp
+++ b/fpdfsdk/fpdfdoc_embeddertest.cpp
@@ -6,6 +6,7 @@
 
 #include "core/fxcrt/include/fx_string.h"
 #include "public/fpdf_doc.h"
+#include "public/fpdf_edit.h"
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
 #include "testing/fx_string_testhelpers.h"
@@ -138,3 +139,10 @@ TEST_F(FPDFDocEmbeddertest, FindBookmarks_bug420) {
       GetFPDFWideString(L"anything");
   EXPECT_EQ(nullptr, FPDFBookmark_Find(document(), title.get()));
 }
+
+TEST_F(FPDFDocEmbeddertest, DeletePage) {
+  EXPECT_TRUE(OpenDocument("hello_world.pdf"));
+  EXPECT_EQ(1, FPDF_GetPageCount(document()));
+  FPDFPage_Delete(document(), 0);
+  EXPECT_EQ(0, FPDF_GetPageCount(document()));
+}