Added missing GetExtraICState() function for CompareICStub. Without it,
code->extra_ic_state() in IC::StateFromCode was returning zero, which was
causing some performance regressions, as the TypeFeedbackInfo was not updated
correctly, resulting in the runtime profiler choosing not to optimise some
functions that we previously would.

BUG=

Review-Url: https://codereview.chromium.org/2116523002
Cr-Commit-Position: refs/heads/master@{#37457}