Bug 1698238 return default dictionary from GetUserMediaRequest#getConstraints() if no constraints are provided r=jib

For the case of a request constructed for "recording-device-stopped".

Differential Revision: https://phabricator.services.mozilla.com/D108373

dom/media/GetUserMediaRequest.cpp

@@ -72,7 +72,12 @@ bool GetUserMediaRequest::IsHandlingUserInput() const {
 }
 
 void GetUserMediaRequest::GetConstraints(MediaStreamConstraints& result) {
-  result = *mConstraints;
+  MOZ_ASSERT(result.mAudio.IsBoolean() && !result.mAudio.GetAsBoolean() &&
+                 result.mVideo.IsBoolean() && !result.mVideo.GetAsBoolean(),
+             "result should be default initialized");
+  if (mConstraints) {
+    result = *mConstraints;
+  }
 }
 
 }  // namespace mozilla::dom

dom/media/GetUserMediaRequest.h

@@ -23,10 +23,12 @@ struct MediaStreamConstraints;
 
 class GetUserMediaRequest : public nsISupports, public nsWrapperCache {
  public:
+  // For "getUserMedia:request"
   GetUserMediaRequest(nsPIDOMWindowInner* aInnerWindow,
                       const nsAString& aCallID,
                       const MediaStreamConstraints& aConstraints,
                       bool aIsSecure, bool aIsHandlingUserInput);
+  // For "recording-device-stopped"
   GetUserMediaRequest(nsPIDOMWindowInner* aInnerWindow, const nsAString& aRawId,
                       const nsAString& aMediaSource, bool aIsHandlingUserInput);