Move pdf_enable_xfa build rules inside pdf_enable_v8 blocks.

V8 is required for XFA. This avoids the possibility of XFA on, V8 off.

Change-Id: I0ed89f6afe6f69e67f9005876bc1bb73b0d77dd5
Reviewed-on: https://pdfium-review.googlesource.com/c/46131
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index e5f2066..990733e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -48,21 +48,21 @@
 
   if (pdf_enable_v8) {
     defines += [ "PDF_ENABLE_V8" ]
-  }
 
-  if (pdf_enable_xfa) {
-    defines += [ "PDF_ENABLE_XFA" ]
-    if (pdf_enable_xfa_bmp) {
-      defines += [ "PDF_ENABLE_XFA_BMP" ]
-    }
-    if (pdf_enable_xfa_gif) {
-      defines += [ "PDF_ENABLE_XFA_GIF" ]
-    }
-    if (pdf_enable_xfa_png) {
-      defines += [ "PDF_ENABLE_XFA_PNG" ]
-    }
-    if (pdf_enable_xfa_tiff) {
-      defines += [ "PDF_ENABLE_XFA_TIFF" ]
+    if (pdf_enable_xfa) {
+      defines += [ "PDF_ENABLE_XFA" ]
+      if (pdf_enable_xfa_bmp) {
+        defines += [ "PDF_ENABLE_XFA_BMP" ]
+      }
+      if (pdf_enable_xfa_gif) {
+        defines += [ "PDF_ENABLE_XFA_GIF" ]
+      }
+      if (pdf_enable_xfa_png) {
+        defines += [ "PDF_ENABLE_XFA_PNG" ]
+      }
+      if (pdf_enable_xfa_tiff) {
+        defines += [ "PDF_ENABLE_XFA_TIFF" ]
+      }
     }
   }