Bug 1271566 - VideoTrackList::RemoveTrack/AddTrack should also update selected index. r=jesup r=pehrsons

MozReview-Commit-ID: Bb4iPGbb9KW

--HG--
extra : transplant_source : %0A%10%5B%26J%93%0E%2C%FD%86%CE%AC%C8%132V%27%F1m8

dom/media/MediaTrackList.h

@@ -45,7 +45,9 @@ public:
 
   void AddTrack(MediaTrack* aTrack);
 
-  void RemoveTrack(const RefPtr<MediaTrack>& aTrack);
+  // In remove track case, the VideoTrackList::mSelectedIndex should be updated
+  // due to mTracks changed. No need to take care this in add track case.
+  virtual void RemoveTrack(const RefPtr<MediaTrack>& aTrack);
 
   void RemoveTracks();
 

dom/media/VideoTrackList.cpp

@@ -23,6 +23,41 @@ VideoTrackList::operator[](uint32_t aIndex)
   return track->AsVideoTrack();
 }
 
+void
+VideoTrackList::RemoveTrack(const RefPtr<MediaTrack>& aTrack)
+{
+  // we need to find the video track before |MediaTrackList::RemoveTrack|. Or
+  // mSelectedIndex will not be valid. The check of mSelectedIndex == -1
+  // need to be done after RemoveTrack. Also the call of
+  // |MediaTrackList::RemoveTrack| is necessary even when mSelectedIndex = -1.
+  bool found;
+  VideoTrack* videoTrack = IndexedGetter(mSelectedIndex, found);
+  MediaTrackList::RemoveTrack(aTrack);
+  if (mSelectedIndex == -1) {
+    // There was no selected track and we don't select another track on removal.
+    return;
+  }
+  MOZ_ASSERT(found, "When mSelectedIndex is set it should point to a track");
+  MOZ_ASSERT(videoTrack, "The mSelectedIndex should be set to video track only");
+
+  // Let the caller of RemoveTrack deal with choosing the new selected track if
+  // it removes the currently-selected track.
+  if (aTrack == videoTrack) {
+    mSelectedIndex = -1;
+    return;
+  }
+
+  // The removed track was not the selected track and there is a
+  // currently-selected video track. We need to find the new location of the
+  // selected track.
+  for (size_t ix = 0; ix < mTracks.Length(); ix++) {
+    if (mTracks[ix] == videoTrack) {
+      mSelectedIndex = ix;
+      return;
+    }
+  }
+}
+
 void
 VideoTrackList::EmptyTracks()
 {

dom/media/VideoTrackList.h

@@ -28,6 +28,8 @@ public:
 
   VideoTrack* operator[](uint32_t aIndex);
 
+  void RemoveTrack(const RefPtr<MediaTrack>& aTrack) override;
+
   void EmptyTracks() override;
 
   // WebIDL