Remove the WTF binary search implementation in favor of std::lower_bound/upper_bound

The binary search implemented in wtf/StdLibExtras.h (we only use the
approximateBinarySearch function) is probably the weirdest binary search
I've seen. If the key is present, it returns a match (arbitrarily if
there are multiple occurrences). If it isn't present, it returns either
the closest value less than the search key or the closest value greater
than it.

This patch changes callers of this binary search to use std::lower_bound
and std::upper_bound (from <algorithm>), and cleans up some of the logic
in the callers.

BUG=

Review URL: https://codereview.chromium.org/122453005

git-svn-id: svn://svn.chromium.org/blink/trunk@164562 bbb929c8-8fbe-4397-9dbb-9b2b20218538