This greatly reduces the number of nodes in the graph (by more than 20x in
some extreme cases) for the Emscripten python interpreter main function.

BUG=v8:3763
LOG=y
TEST=cctest,mjsunit,unittests
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/802353003

Cr-Commit-Position: refs/heads/master@{#25840}