Process XFA preamble by inclusion rather than hard-coded strings

Change-Id: I44d58ce553712face3377ae24d93576a29954c4c
Reviewed-on: https://pdfium-review.googlesource.com/c/45490
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/testing/resources/xfa_object_2_0.fragment b/testing/resources/xfa_object_2_0.fragment
new file mode 100644
index 0000000..c8b5a34
--- /dev/null
+++ b/testing/resources/xfa_object_2_0.fragment
@@ -0,0 +1,15 @@
+{{object 2 0}} <<
+  /XFA [
+    (preamble)
+    3 0 R
+    (config)
+    4 0 R
+    (template)
+    5 0 R
+    (localeSet)
+    6 0 R
+    (postamble)
+    7 0 R
+  ]
+>>
+endobj