Chrome Version:
Chromium	66.0.3330.0 (Developer Build) (64-bit)
Revision	e3882dbe4ca8dc822bbb6549428208cf278d703d-refs/heads/master@{#531359}
OS: Linux

What steps will reproduce the problem?
(0) Compile a Debug build
(1) Visit https://www.google.com/webmasters/
(2) Click "Search Console" button
(3) After auth page finishes loading, hit Back, wait for previous page to finish loading.

What is the expected result?
Previous page loads with no problems.

What happens instead?
DCHECK failure
[204246:204246:0123/124333.042166:FATAL:page_load_metrics_util.cc(56)] Check failed: query[0] != '?' && query[0] != '#'.

This happens because page_load_metrics::IsGoogleSearchResultUrl() called on "https://www.google.com/webmasters/#?modal_active=none" results in a call to QueryContainsComponentHelper with a query (ref) of "?modal_active=none". The DCHECK, intending to verify that GURL::query_piece() and GURL::ref_piece() are written correctly, incorrectly catches this valid ref string.

I've written a quick CL that adds a regression test case to PageLoadMetricsUtilTest.IsGoogleSearchResultUrl, and removes the DCHECK: https://crrev.com/c/882211

I think the goal of the DCHECK is better served by existing unittests, and that if GURL breaks conformance to the URL spec then a lot of other things break as well.

Another option would be to split the query and the ref case of the DCHECK into two separate checks to verify the conformance of url.query_piece() and url.ref_piece() before passing them to QueryContainsComponentHelper.