Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES.

components/page_load_metrics/browser/metrics_web_contents_observer.cc

 // Copyright 2015 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 "components/page_load_metrics/browser/metrics_web_contents_observer.h"
 
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "components/page_load_metrics/common/page_load_metrics_messages.h"
 #include "components/page_load_metrics/common/page_load_timing.h"
@@ skipping 31 matching lines @@
 }
 
 bool IsValidPageLoadTiming(const PageLoadTiming& timing) {
   if (timing.IsEmpty())
     return false;
 
   // If we have a non-empty timing, it should always have a navigation start.
   DCHECK(!timing.navigation_start.is_null());
 
   // If we have a DOM content loaded event, we should have a response start.
-  DCHECK(timing.dom_content_loaded_event_start.is_zero() ||
-         timing.response_start <= timing.dom_content_loaded_event_start);
+  DCHECK_IMPLIES(
+      !timing.dom_content_loaded_event_start.is_zero(),
+      timing.response_start <= timing.dom_content_loaded_event_start);
 
   // If we have a load event, we should have both a response start and a DCL.
   // TODO(csharrison) crbug.com/536203 shows that sometimes we can get a load
   // event without a DCL. Figure out if we can change this condition to use a
   // DCHECK instead.
   if (!timing.load_event_start.is_zero() &&
       (timing.dom_content_loaded_event_start.is_zero() ||
        timing.response_start > timing.load_event_start ||
        timing.dom_content_loaded_event_start > timing.load_event_start)) {
     return false;
@@ skipping 291 matching lines @@
 
   if (!committed_load_->UpdateTiming(timing)) {
     // If the page load tracker cannot update its timing, something is wrong
     // with the IPC (it's from another load, or it's invalid in some other way).
     // We expect this to be a rare occurrence.
     RecordInternalError(ERR_BAD_TIMING_IPC);
   }
 }
 
 }  // namespace page_load_metrics