frame->GetExpression always returns the same function. We should iterate through expression stack when we use Function.call.apply for finding actual target.

LOG=N
BUG=chromium:499479
R=yurys@chromium.org,yangguo@chromium.org

Review URL: https://codereview.chromium.org/1182703003

Cr-Commit-Position: refs/heads/master@{#29048}