[Page Load Metrics] Add mojom file to page load metrics.

chrome/browser/page_load_metrics/page_load_tracker.h

 // 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.
 
 #ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 357 matching lines @@
 
   base::TimeTicks page_end_time_;
 
   // We record separate metrics for events that occur after a background,
   // because metrics like layout/paint are delayed artificially
   // when they occur in the background.
   base::TimeTicks background_time_;
   base::TimeTicks foreground_time_;
   bool started_in_foreground_;
 
-  PageLoadTiming timing_;
+  mojo::StructPtr<PageLoadTiming> timing_;
   PageLoadMetadata main_frame_metadata_;
   PageLoadMetadata child_frame_metadata_;
 
   ui::PageTransition page_transition_;
 
   base::Optional<content::GlobalRequestID> navigation_request_id_;
 
   // Whether this page load was user initiated.
   UserInitiatedInfo user_initiated_info_;
 
@@ skipping 13 matching lines @@
   PageLoadMetricsEmbedderInterface* const embedder_interface_;
 
   std::vector<std::unique_ptr<PageLoadMetricsObserver>> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(PageLoadTracker);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_