Inflict PDF_ENABLE_XFA ifdefs on XFA fpdfsdk/

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1477583002 .
diff --git a/fpdfsdk/src/javascript/JS_Runtime.h b/fpdfsdk/src/javascript/JS_Runtime.h
index 2353517..6de2b70 100644
--- a/fpdfsdk/src/javascript/JS_Runtime.h
+++ b/fpdfsdk/src/javascript/JS_Runtime.h
@@ -58,12 +58,14 @@
   v8::Isolate* GetIsolate() const { return m_isolate; }
   v8::Local<v8::Context> NewJSContext();
 
+#ifdef PDF_ENABLE_XFA
   // IJS_Runtime:
   FX_BOOL GetHValueByName(const CFX_ByteStringC& utf8Name,
                           FXJSE_HVALUE hValue) override;
   FX_BOOL SetHValueByName(const CFX_ByteStringC& utf8Name,
                           FXJSE_HVALUE hValue) override;
 
+#endif
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);