When we inlined a [[Construct]] call to a subclass constructor, we can
also inline the super constructor call (either explicit or implicit),
since we have a concrete JSFunction constant for the subclass and we
can thus constant-fold the %_GetSuperConstructor intrinsic. We don't
need any guards here since the prototype of subclass constructors is
non-writable, non-configurable in ES6.

BUG=v8:5517
R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2409423006
Cr-Commit-Position: refs/heads/master@{#40261}