1. Use a reverse_range() adaptor for range-based reverse iteration through containers.
2. Remove the emitting of the commented llvm-mc command line.
3. Remove a few TODOs.
4. For commented-out declarations within a class T like this:
// T(const T&) = delete;
// T &operator=(const T &) = delete;
Replace them with this:
T(const T&) = default;
T &operator=(const T &) = default;
And try to keep them private where possible.
5. Make LivenessNode and TimerTreeNode into internal classes.
BUG= none
R=jvoung@chromium.org
Review URL: https://codereview.chromium.org/830303003
