Fixed the dependency between 'summarize' and 'model'.
Fixed the dependency between 'summarize' and 'model'.

Since `summarize` captures the important fields of an object, `model`
will always be a superset of it.
We can see that `model(const Framework&)` calls
`summarize(const Framework&)` and augments additional fields.

This patch removes the unnecessary forward declaration and makes
`model(const Slave&)` depend on `summarize(const Slave&)` instead.

Review: https://reviews.apache.org/r/34378

dforsyth/mesos,yuquanshan/customizedMesos,craimbert/mesos,craimbert/mesos,andschwa/mesos,asamerh4/mesos,gsantovena/mesos,jpeach/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,jpeach/mesos,verizonlabs/mesos,craimbert/mesos,dforsyth/mesos,kaysoky/mesos,Gilbert88/mesos,gsantovena/mesos,verizonlabs/mesos,dforsyth/mesos,asamerh4/mesos,yuquanshan/customizedMesos,abudnik/mesos,craimbert/mesos,neilconway/mesos,zmalik/mesos,Aman-Jain-14/customizedMesos,zmalik/mesos,craimbert/mesos,Aman-Jain-14/customizedMesos,kaysoky/mesos,neilconway/mesos,neilconway/mesos,jpeach/mesos,jpeach/mesos,kaysoky/mesos,abudnik/mesos,chhsia0/mesos,abudnik/mesos,asamerh4/mesos,Aman-Jain-14/customizedMesos,reneploetz/mesos,chhsia0/mesos,Gilbert88/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,verizonlabs/mesos,reneploetz/mesos,kaysoky/mesos,gsantovena/mesos,asamerh4/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,jpeach/mesos,dforsyth/mesos,kaysoky/mesos,andschwa/mesos,zmalik/mesos,zmalik/mesos,andschwa/mesos,dforsyth/mesos,abudnik/mesos,gsantovena/mesos,yuquanshan/customizedMesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,dforsyth/mesos,abudnik/mesos,abudnik/mesos,kaysoky/mesos,asamerh4/mesos,andschwa/mesos,yuquanshan/customizedMesos,neilconway/mesos,jpeach/mesos,reneploetz/mesos,reneploetz/mesos,reneploetz/mesos,andschwa/mesos,verizonlabs/mesos,andschwa/mesos,gsantovena/mesos,andschwa/mesos,abudnik/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,reneploetz/mesos,zmalik/mesos,Gilbert88/mesos,jpeach/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,zmalik/mesos,chhsia0/mesos,chhsia0/mesos,craimbert/mesos,asamerh4/mesos,verizonlabs/mesos,neilconway/mesos,Gilbert88/mesos,Gilbert88/mesos,chhsia0/mesos,neilconway/mesos,neilconway/mesos,verizonlabs/mesos,asamerh4/mesos,craimbert/mesos,verizonlabs/mesos,yuquanshan/customizedMesos,zmalik/mesos,gsantovena/mesos,kaysoky/mesos,reneploetz/mesos