Stop logging Extensions.ShouldAllowOpenURL.Failure* histograms.

These histograms were added 2.5+ years ago as part of fixing a
security issue in https://crbug.com/656752, in the following CLs:
  https://codereview.chromium.org/2787573003
  https://codereview.chromium.org/2454563003

Per offline chat with creis@ and lukasza@, we've agreed that these
histograms are no longer useful, so this CL removes the fairly complex
logging logic as well as the associated tests and presubmit code.  It
also removes a closely related DumpWithoutCrashing call that we no
longer need.

Bug: 975510
Change-Id: I30bbbb538c23603372968c38f312c4b52be53d6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1696762
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Alex Moshchuk <alexmos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#677575}
9 files changed