Tidy PDF_ENABLE_XFA #ifdefs in fpdfsdk.

-- label matching #endifs
-- prefer #ifdef over #ifndef
-- consolidate some blocks.

R=ochang@chromium.org

Review URL: https://codereview.chromium.org/1484843002 .
diff --git a/fpdfsdk/include/javascript/IJavaScript.h b/fpdfsdk/include/javascript/IJavaScript.h
index 7eab25f..0ce866c 100644
--- a/fpdfsdk/include/javascript/IJavaScript.h
+++ b/fpdfsdk/include/javascript/IJavaScript.h
@@ -7,12 +7,13 @@
 #ifndef FPDFSDK_INCLUDE_JAVASCRIPT_IJAVASCRIPT_H_
 #define FPDFSDK_INCLUDE_JAVASCRIPT_IJAVASCRIPT_H_
 
-#ifdef PDF_ENABLE_XFA
-#include "../../../xfa/include/fxjse/fxjse.h"
-#endif
 #include "core/include/fxcrt/fx_string.h"
 #include "core/include/fxcrt/fx_system.h"
 
+#ifdef PDF_ENABLE_XFA
+#include "../../../xfa/include/fxjse/fxjse.h"
+#endif  // PDF_ENABLE_XFA
+
 class CPDFDoc_Environment;
 class CPDFSDK_Annot;
 class CPDFSDK_Document;
@@ -156,8 +157,8 @@
                                   FXJSE_HVALUE hValue) = 0;
   virtual FX_BOOL SetHValueByName(const CFX_ByteStringC& utf8Name,
                                   FXJSE_HVALUE hValue) = 0;
+#endif  // PDF_ENABLE_XFA
 
-#endif
  protected:
   IJS_Runtime() {}
 };