On Win 7 in a debug configuration, this was gathering hundreds of
thousands of locks, causing test timeouts to be exceeded. On user
machines, UnhandledExceptionHandler() probably would have timed out
also. Arbitrarily cap the number of locks captured, as we don't have a
pressing need for anything other than the LoaderLock anyway.
In the future, we may want to figure out a signalling mechanism so that
the client can note other interesting locks to be grabbed, and just
avoid walking the list entirely.
R=mark@chromium.org
BUG=chromium:546288
Review URL: https://codereview.chromium.org/1475033005 .