Make calls like

  new Array(n)
  new A(n)

(where A is a subclass of Array) inlinable into TurboFan. We do this by
speculatively checking that n is an unsigned integer that is not greater
than JSArray::kInitialMaxFastElementArray, and then lowering the backing
store allocation to a builtin call. The speculative optimization is
either protected by the AllocationSite for the Array constructor
invocation (if we have one), or by a newly introduced global protector
cell that is used for Array constructor invocations that don't have an
AllocationSite, i.e. the ones from Array#map, Array#filter, or from
subclasses of Array.

Next step will be to implement the backing store allocations inline in
TurboFan, but that requires Loop support in the GraphAssembler, so it's
done as a separate CL. This should further boost the performance.

This boosts the ARES6 ML benchmark by up to 8% on the steady state,
and also improves monomorphic Array#map calls by around 20-25% on the
initial setup.

Bug: v8:6399
Tbr: ulan@chromium.org
Change-Id: I7c8bdecf7c814ce52db6ee3051c3206a4f7d4bb6
Reviewed-on: https://chromium-review.googlesource.com/704639
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48348}