Cleanup the fx_extension code.

This CL cleans up the fx_extension file. The stream code was moved to
fx_stream. IFX_FileAccess was removed and CFX_CRTFileAccess split to its
own file. Code shuffled from header to cpp file.

Change-Id: I700fdfcc9797cf4e8050cd9ba010ad8854feefbf
Reviewed-on: https://pdfium-review.googlesource.com/4371
Reviewed-by: Nicolás Peña <npm@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
diff --git a/fpdfsdk/javascript/util.cpp b/fpdfsdk/javascript/util.cpp
index f88cdc6..4303342 100644
--- a/fpdfsdk/javascript/util.cpp
+++ b/fpdfsdk/javascript/util.cpp
@@ -12,7 +12,7 @@
 #include <string>
 #include <vector>
 
-#include "core/fxcrt/fx_ext.h"
+#include "core/fxcrt/fx_extension.h"
 #include "fpdfsdk/javascript/JS_Define.h"
 #include "fpdfsdk/javascript/JS_EventHandler.h"
 #include "fpdfsdk/javascript/JS_Object.h"