Document that frame summaries are bottom-to-top, i.e. caller before
callee, rename FrameSummary::GetFirst to FrameSummary::GetBottom and
introduce FrameSummary::GetTop.
For debugged JavaScript frames, it does not really matter which of the
functions we call, so I replaced a few GetFirst by GetTop instead of
GetBottom because it matches the semantics more closely.

This CL also reverts part of http://crrev.com/2621953002 by changing
BreakLocation::FromFrame back to accept a DebugInfo and a
JavaScriptFrame. We don't plan to create BreakLocations for wasm.

R=yangguo@chromium.org
BUG=v8:5822

Review-Url: https://codereview.chromium.org/2647433002
Cr-Commit-Position: refs/heads/master@{#42505}