[PageLoadMetrics] Don't record an ads histogram if the page hasn't committed

chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer.h

 // Copyright 2017 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_OBSERVERS_ADS_PAGE_LOAD_METRICS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_ADS_PAGE_LOAD_METRICS_OBSERVER_H_
 
 #include <list>
 #include <map>
 #include <memory>
@@ skipping 55 matching lines @@
   std::map<FrameTreeNodeId, AdFrameData*> ad_frames_data_;
 
   // When the observer receives report of a document resource loading for a
   // sub-frame before the sub-frame commit occurs, hold onto the resource
   // request info (delay it) until the sub-frame commits.
   std::map<FrameTreeNodeId, page_load_metrics::ExtraRequestCompleteInfo>
       ongoing_navigation_resources_;
 
   size_t page_bytes_ = 0u;
   size_t uncached_page_bytes_ = 0u;
+  bool committed_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(AdsPageLoadMetricsObserver);
 };
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_ADS_PAGE_LOAD_METRICS_OBSERVER_H_