Remove dom_loading from page_load_metrics

chrome/common/page_load_metrics/page_load_timing.h

 // 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.
 
 #ifndef CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_TIMING_H_
 #define CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_TIMING_H_
 
 #include "base/optional.h"
 #include "base/time/time.h"
 #include "third_party/WebKit/public/platform/WebLoadingBehaviorFlag.h"
@@ skipping 17 matching lines @@
   bool IsEmpty() const;
 
   // Time that the navigation for the associated page was initiated.
   base::Time navigation_start;
 
   // All TimeDeltas are relative to navigation_start
 
   // Time that the first byte of the response is received.
   base::Optional<base::TimeDelta> response_start;
 
-  // Time that the document transitions to the 'loading' state. This is roughly
-  // the time that the HTML parser begins parsing the main HTML resource.
-  base::Optional<base::TimeDelta> dom_loading;
-
   // Time immediately before the DOMContentLoaded event is fired.
   base::Optional<base::TimeDelta> dom_content_loaded_event_start;
 
   // Time immediately before the load event is fired.
   base::Optional<base::TimeDelta> load_event_start;
 
   // Time when the first layout is completed.
   base::Optional<base::TimeDelta> first_layout;
 
   // Time when the first paint is performed.
@@ skipping 34 matching lines @@
 struct PageLoadMetadata {
   PageLoadMetadata();
   bool operator==(const PageLoadMetadata& other) const;
   // These are packed blink::WebLoadingBehaviorFlag enums.
   int behavior_flags = blink::WebLoadingBehaviorNone;
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_TIMING_H_