Add DCHECK to show that plznav sometimes provides empty global request ids.

chrome/browser/page_load_metrics/page_load_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/page_load_tracker.h"
 
 #include <algorithm>
 #include <ostream>
 #include <string>
 #include <utility>
@@ skipping 413 matching lines @@
   }
 
   INVOKE_AND_PRUNE_OBSERVERS(observers_, OnShown);
 }
 
 void PageLoadTracker::WillProcessNavigationResponse(
     content::NavigationHandle* navigation_handle) {
   // PlzNavigate: NavigationHandle::GetGlobalRequestID() sometimes returns an
   // uninitialized GlobalRequestID. Bail early in this case. See
   // crbug.com/680841 for details.
+  DCHECK(navigation_handle->GetGlobalRequestID() != content::GlobalRequestID());
   if (content::IsBrowserSideNavigationEnabled() &&
       navigation_handle->GetGlobalRequestID() == content::GlobalRequestID())
     return;
 
   DCHECK(!navigation_request_id_.has_value());
   navigation_request_id_ = navigation_handle->GetGlobalRequestID();
   DCHECK(navigation_request_id_.value() != content::GlobalRequestID());
 }
 
 void PageLoadTracker::Commit(content::NavigationHandle* navigation_handle) {
@@ skipping 249 matching lines @@
   // user initiated.
   if (abort_type != ABORT_CLIENT_REDIRECT)
     abort_user_initiated_info_ = user_initiated_info;
 
   if (is_certainly_browser_timestamp) {
     ClampBrowserTimestampIfInterProcessTimeTickSkew(&abort_time_);
   }
 }
 
 }  // namespace page_load_metrics