Note that this is just a duplication for now. We'll want to get rid of the
NodeProperties::ReplaceWithValue() method in the long run.
R=bmeurer@chromium.org
BUG=
Review URL: https://codereview.chromium.org/1135483004
Cr-Commit-Position: refs/heads/master@{#28363}
An AdvancedReducer is basically a regular Reducer with an editor
that can perform graph editing operations beyond changing or
replacing the node that is currently being reduced. The GraphReducer
is the default implementation of the AdvancedReducer::Editor interface.
The ControlReducerImpl is now just an AdvancedReducer, which
temporarily requires a Finish method in the reducer to implement
the dead node trimming until we move that to the GraphReducer
(which in turn requires that all loops are connected to End).
Review URL: https://codereview.chromium.org/1122423003
Cr-Commit-Position: refs/heads/master@{#28251}
