Previously we first created a temporary graph for the inlinee and then
copied over all the nodes to the actual graph. This however introduces
unnecessary complexity, and we can instead just create the inlinee
inside the target graph.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2006353003
Cr-Commit-Position: refs/heads/master@{#36508}