Fix behaviour of app.alert() with a single object argument.

fpdfsdk/src/javascript/JS_Value.h

Index: fpdfsdk/src/javascript/JS_Value.h
diff --git a/fpdfsdk/src/javascript/JS_Value.h b/fpdfsdk/src/javascript/JS_Value.h
index 20a6e38b46965e9cac89264d676b634f285b5492..c33a973a12a236768e788cadb94eb147507c24dc 100644
--- a/fpdfsdk/src/javascript/JS_Value.h
+++ b/fpdfsdk/src/javascript/JS_Value.h
@@ -213,4 +213,16 @@ double JS_MakeDate(double day, double time);
 bool JS_PortIsNan(double d);
 double JS_LocalTime(double d);
 
+// Some JS methods have the bizarre convention that they may also be called
+// with a single argument which is an object containing the actual arguments
+// as its properties. The varying arguments to this method are the property
+// names as wchar_t string literals corresponding to each positional argument.
+// The result will always contain |nKeywords| value, with unspecified ones
+// being set to type VT_unknown.
+std::vector<CJS_Value> JS_ExpandKeywordParams(
+    CJS_Runtime* pRuntime,
+    const std::vector<CJS_Value>& originals,
+    size_t nKeywords,
+    ...);
+
 #endif  // FPDFSDK_SRC_JAVASCRIPT_JS_VALUE_H_