chrome: Cleanup class/struct forward declarations

chrome/browser/page_load_metrics/page_load_metrics_util.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_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UTIL_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UTIL_H_
 
 #include "base/metrics/histogram_macros.h"
 #include "base/optional.h"
 #include "base/time/time.h"
 
 #define PAGE_LOAD_HISTOGRAM(name, sample)                           \
   UMA_HISTOGRAM_CUSTOM_TIMES(name, sample,                          \
                              base::TimeDelta::FromMilliseconds(10), \
                              base::TimeDelta::FromMinutes(10), 100)
 
 namespace page_load_metrics {
 
 struct PageLoadExtraInfo;
-struct PageLoadTiming;
 
 // Returns true if:
 // - We have timing information for the event.
 // - The page load started while the page was in the foreground.
 // - The event occurred prior to the page being moved to the background.
 // When a page is backgrounded, some events (e.g. paint) are delayed. Since
 // these data points can skew the mean, they should not be mixed with timing
 // events that occurred in the foreground.
 // If the event time delta and background time delta are equal, we still
 // consider the event to be logged in the foreground histogram since any
 // background specific handling would not yet have been applied to that event.
 bool WasStartedInForegroundOptionalEventInForeground(
     const base::Optional<base::TimeDelta>& event,
     const PageLoadExtraInfo& info);
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UTIL_H_