Disable UserInputTracker DCHECK which is firing in unit tests.

chrome/browser/page_load_metrics/user_input_tracker.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/page_load_metrics/user_input_tracker.h"
 
 #include <algorithm>
 
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 
@@ skipping 81 matching lines @@
   // can be used to distinguish these cases. isTrusted isn't yet a property of
   // WebInputEvent. We should consider adding it.
 
   const base::TimeTicks now = base::TimeTicks::Now();
   base::TimeTicks time = RoundToRateLimitedOffset(GetEventTime(event));
   if (time <=
       std::max(most_recent_consumed_time_, now - GetOldEventThreshold()))
     return;
 
   if (time > now) {
-    DCHECK(!base::TimeTicks::IsHighResolution());
+    // We should never receive a UserInputEvent with a timestamp in the future
+    // if we're on a platform with a high-res clock, where the monotonic clock
+    // is system-wide monotonic. Unfortunately, this DCHECK seems to fire in
+    // some linux unit tests, so it is disabled for the time being. See
+    // crbug.com/678093 for more details.
+    // DCHECK(!base::TimeTicks::IsHighResolution());
     return;
   }
 
   // lower_bound finds the first element >= |time|.
   auto it = std::lower_bound(sorted_event_times_.begin(),
                              sorted_event_times_.end(), time);
   if (it != sorted_event_times_.end() && *it == time) {
     // Don't insert duplicate values.
     return;
   }
@@ skipping 54 matching lines @@
       std::upper_bound(sorted_event_times_.begin(), sorted_event_times_.end(),
                        cutoff));
 }
 
 // static
 base::TimeDelta UserInputTracker::GetOldEventThreshold() {
   return base::TimeDelta::FromSeconds(kOldestAllowedEventAgeSeconds);
 }
 
 }  // namespace page_load_metrics