This adapts the aformentioned interface to no longer return a list of
{JSFunction} objects, but {SharedFunctionInfo} objects instead. Since
deoptimization data only contains the latter as literals, this by now
represents the fast path. All call sites requiring the former can use
the slow path via {JavaScriptFrame::Summarize} instead.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2626213002
Cr-Commit-Position: refs/heads/master@{#42311}