Utilize the string length protector to deoptimize if the resulting
string length for string addition overflows. This way we generate
less code here and avoid holding on to the lazy frame state, and
thus potentially reduce the number live ranges.

BUG=v8:5267,v8:5404
R=yangguo@chromium.org

Review-Url: https://codereview.chromium.org/2491943004
Cr-Commit-Position: refs/heads/master@{#40909}