Add ContainsKey() and ContainsValue() and use them where appropriate.

fpdfsdk/src/javascript/util.cpp

Index: fpdfsdk/src/javascript/util.cpp
diff --git a/fpdfsdk/src/javascript/util.cpp b/fpdfsdk/src/javascript/util.cpp
index cb9c9b22317e07a4d90707c3e7835ddc6ff010ae..a14e81c203e40b7fbcffccd1e37cf55eedabe4e2 100644
--- a/fpdfsdk/src/javascript/util.cpp
+++ b/fpdfsdk/src/javascript/util.cpp
@@ -468,17 +468,13 @@ void util::printx(const std::string& cFormat,
       case '\\':
         break;
       case '>': {
-        for (std::string::iterator it = cSource.begin(); it != cSource.end();
-             it++) {
-          *it = toupper(*it);
-        }
+        for (char& c : cSource)
+          c = toupper(c);
         break;
       }
       case '<': {
-        for (std::string::iterator it = cSource.begin(); it != cSource.end();
-             it++) {
-          *it = tolower(*it);
-        }
+        for (char& c : cSource)
+          c = tolower(c);
         break;
       }
       case '=':