We have the BytecodeIterator with next() and has_next() methods, and
pc_offset() and current() accessors.
This CL adds an interface to iterate over the opcodes or offsets in a
C++ foreach loop.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2587143002
Cr-Commit-Position: refs/heads/master@{#41851}