We will subsequently treat the whole profile as "flat" in the frontend, (i.e flatten and combine with the flat profile section), so we can have a profile for ThinLTO for parts of the application that don't come under the contextual profile. After ThinLTO, we will treat the module(s) containing contextual trees differently: they'll have only the contextual profile pertinent to them. The rest of the modules (non-contextual) will proceed "as usual", off the flattened profile.
This patch implements pruning of the contextual profile to enable the above.
6a3e5f89bb