This CL also adds speculation to all Math builtins,
and refactors the JSCallReducer.

Bug: v8:7250, v8:7240
Change-Id: Icdaddb767e875bb191939d907f65c7a8dcf79b8b
Reviewed-on: https://chromium-review.googlesource.com/873916
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51426}