Use counter for mixing old and new constraints

third_party/WebKit/Source/modules/mediastream/MediaConstraintsImpl.cpp

Index: third_party/WebKit/Source/modules/mediastream/MediaConstraintsImpl.cpp
diff --git a/third_party/WebKit/Source/modules/mediastream/MediaConstraintsImpl.cpp b/third_party/WebKit/Source/modules/mediastream/MediaConstraintsImpl.cpp
index 360f7b4c6f8a308c0adcc55feab1a75d52e95c51..a7b2b5df1133117879fe8d2f50d8ad549826f36c 100644
--- a/third_party/WebKit/Source/modules/mediastream/MediaConstraintsImpl.cpp
+++ b/third_party/WebKit/Source/modules/mediastream/MediaConstraintsImpl.cpp
@@ -602,6 +602,7 @@ WebMediaConstraints create(ExecutionContext* context, const MediaTrackConstraint
     WebMediaConstraints standardForm = convertConstraintsToWeb(constraintsIn);
     if (constraintsIn.hasOptional() || constraintsIn.hasMandatory()) {
         if (!standardForm.isEmpty()) {
+            UseCounter::count(context, UseCounter::MediaStreamConstraintsOldAndNew);
             errorState.throwTypeError("Malformed constraint: Cannot use both optional/mandatory and specific or advanced constraints.");
             return WebMediaConstraints();
         }