Forward declare more in xfa_js_embedder_test.h.

Remove includes for xfa/ that are not strictly needed. Instead, forward
declare XFA and V8 classes, and do IWYU as necessary. This avoids
transitively including V8 headers in xfa_js_embedder_test.h.

Change-Id: I9c5cddf27d99faf50e9e8e2ffe0584fff878cc4c
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/70432
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>

testing/xfa_js_embedder_test.h

diff --git a/testing/xfa_js_embedder_test.h b/testing/xfa_js_embedder_test.h
index 412ffd9..d861389 100644
--- a/testing/xfa_js_embedder_test.h
+++ b/testing/xfa_js_embedder_test.h
@@ -8,13 +8,17 @@
 #include <memory>
 #include <string>
 
+#include "core/fxcrt/string_view_template.h"
 #include "testing/embedder_test.h"
-#include "xfa/fxfa/parser/cxfa_document.h"
-#include "xfa/fxfa/parser/cxfa_node.h"
 
 class CFXJSE_Engine;
 class CFXJSE_Value;
 class CFX_V8ArrayBufferAllocator;
+class CXFA_Document;
+
+namespace v8 {
+class Isolate;
+}
 
 class XFAJSEmbedderTest : public EmbedderTest {
  public: