Cleaning up MruWindowTracker::BuildWindowList()
Removing the top_most_at_end parameter which was always set to false and
was never used.
The previous CL (https://codereview.chromium.org/
752253002) was reverted as it caused ash_unittests to fail on Windows:
http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20(dbg)(1)
http://build.chromium.org/p/chromium.win/builders/Win8%20Aura
This is a retry, but we keep reversing the windows list after we build it.
R=oshima@chromium.org
BUG=None
Review URL: https://codereview.chromium.org/
785273002
Cr-Commit-Position: refs/heads/master@{#307593}