There is no compositor when we use webrender for composition(we will use RenderOGL which is not inherit from compositor). And we also want to add more webrender specific things(e.g. we will have renader thread) for CompositableHost. So, I'm trying to split CompositableOperation related functions into a CompositableHostBase(I don't have a good name right now) and use this new base class in CompositableParentManager::ReceiveCompositableUpdate(). CompositableHost will have all compositor related functions, and WebrenderCompositableHost will only have webrender specific logic. The class diagram will be: CompositableHostBase <----- WebrenderCompositableHost ^ | +----------- CompositableHost

MozReview-Commit-ID: GD4JKbpgcfT

I create a base class CompositableBase for both CompositableHost and WebrenderCompositableHost. It has to method: AsCompositableHost() and AsWebrenderCompositableHost(). That could be used for original gecko code or WR specific flow. Any comment here?

I prefer not to have CompositableBase for now, since we are going to have only WebRenderImageHost as WebrenderCompositableHost. In Bug 1336021, I created WebRenderImageHost, it looks simple enough without CompositableBase.

I just thought that creating CompositableBase might be too much just for WebRenderImageHost.

With bug 1336021, there is no need to have this approach.