[WIP] bindings: Introduce PropertyBag

Source/modules/mediastream/MediaConstraintsImpl.cpp

Index: Source/modules/mediastream/MediaConstraintsImpl.cpp
diff --git a/Source/modules/mediastream/MediaConstraintsImpl.cpp b/Source/modules/mediastream/MediaConstraintsImpl.cpp
index cc9f7f5eb3a7baf2a48ff75059da4edf4f48c7c0..c1ae7eabb44c8e5d421e70a76e8ae8cf742da87a 100644
--- a/Source/modules/mediastream/MediaConstraintsImpl.cpp
+++ b/Source/modules/mediastream/MediaConstraintsImpl.cpp
@@ -80,7 +80,7 @@ static bool parse(const Dictionary& constraintsDictionary, WebVector<WebMediaCon
     Vector<WebMediaConstraint> optionalConstraintsVector;
     if (names.contains(optionalName)) {
         ArrayValue optionalConstraints;
-        bool ok = DictionaryHelper::get(constraintsDictionary, optionalName, optionalConstraints);
+        bool ok = constraintsDictionary.get(optionalName, optionalConstraints);
         if (!ok || optionalConstraints.isUndefinedOrNull())
             return false;
 
@@ -100,7 +100,7 @@ static bool parse(const Dictionary& constraintsDictionary, WebVector<WebMediaCon
                 return false;
             String key = localNames[0];
             String value;
-            ok = DictionaryHelper::get(constraint, key, value);
+            ok = constraint.get(key, value);
             if (!ok)
                 return false;
             optionalConstraintsVector.append(WebMediaConstraint(key, value));