Blender Git Loki

Fix T77997: GPencil insert keyframe on timeline doen't update viewport

The reason was the datablock is changed but it was not tagged for depsgraph refresh.

In some cases it could be possible to tag several times the same datablock, but as this is not the case all the times and the number of tags is always very small, it doesn't worth a complex code to keep a memory list of the datablocks to tag.