GitLab

In a prior CL [1], I added the CheckIdempotency() function, which tests
that GURL canonicalization produces a fixed point the first time it's
called.

There was some confusion whether CheckIdempotency was duplicating logic
that already existed in the fuzzer; the fuzzer already had a few lines
to copy the GURL with a no-op call to ReplaceComponents and check that
the spec string is unchanged.

This "copy check" is subtly different than the idempotency check. In
particular, it cannot catch the "file:///.//" -> "file:////" ->
"file:///" bug because it never reaches DoParseFileURL.

For context, the non-idempotency bug for "file:///.//" arises because
  * DoPartialPath drops "./", taking "file:///.//" to "file:////"
  * DoParseFileURL collapses "//" to "/", taking "file:////" to
    "file:///".

[1]: http://crrev.com/c/2414615

Bug: 1128999
Change-Id: Ib35982f56cac3ced23d13def74f073a0245bdee3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2424764Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Vaclav Brozek <vabr@chromium.org>
Commit-Queue: Dan McArdle <dmcardle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810286}