This simplifies the calling convention of LoadGlobalIC.

Currently we do a linear search to get the name but I'll address this in a follow-up CL.

BUG=chromium:576312
TBR=rossberg@chromium.org

Review-Url: https://codereview.chromium.org/2084913006
Cr-Commit-Position: refs/heads/master@{#37253}