Small tidy of fxjs

Use correct include style for v8 headers.
Use incomplete type to avoid including header.

Change-Id: Ibd58aa25b2a17fbd1cf6a20643b6f25ca008974f
Reviewed-on: https://pdfium-review.googlesource.com/25230
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/fxjs/cjs_v8.h b/fxjs/cjs_v8.h
index 1dd4953..1a8d15b 100644
--- a/fxjs/cjs_v8.h
+++ b/fxjs/cjs_v8.h
@@ -7,15 +7,14 @@
 #ifndef FXJS_CJS_V8_H_
 #define FXJS_CJS_V8_H_
 
-#include <v8-util.h>
-#include <v8.h>
-
 #include <map>
 #include <vector>
 
 #include "core/fxcrt/bytestring.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/widestring.h"
+#include "v8/include/v8-util.h"
+#include "v8/include/v8.h"
 
 #ifdef PDF_ENABLE_XFA
 class CXFA_Object;