Create LoadingDataCollector class and have observers rely on it instead of ResourcePrefetchPredictor

chrome/browser/page_load_metrics/observers/resource_prefetch_predictor_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/resource_prefetch_predictor_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/resource_prefetch_predictor_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/resource_prefetch_predictor_page_load_metrics_observer.cc
index e0c4309fde956779c992614c08977897774a899e..0ea021458462becfaf1cd2e70b8355231f62413e 100644
--- a/chrome/browser/page_load_metrics/observers/resource_prefetch_predictor_page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/observers/resource_prefetch_predictor_page_load_metrics_observer.cc
@@ -34,17 +34,20 @@ ResourcePrefetchPredictorPageLoadMetricsObserver::CreateIfNeeded(
   if (!loading_predictor)
     return nullptr;
   return base::MakeUnique<ResourcePrefetchPredictorPageLoadMetricsObserver>(
-      loading_predictor->resource_prefetch_predictor(), web_contents);
+      loading_predictor->resource_prefetch_predictor(),
+      loading_predictor->glowplug_collector(), web_contents);
 }
 
 ResourcePrefetchPredictorPageLoadMetricsObserver::
     ResourcePrefetchPredictorPageLoadMetricsObserver(
         predictors::ResourcePrefetchPredictor* predictor,
+        predictors::GlowplugCollector* collector,
         content::WebContents* web_contents)
     : predictor_(predictor),
+      collector_(collector),
       web_contents_(web_contents),
       record_histograms_(false) {
-  DCHECK(predictor_);
+  DCHECK(collector_);

[alexilin, 2017/05/22 13:20:36]

nit:
Why do not check both? The implementation detail that collector contains a
pointer to predictor shouldn't affect this code.

[trevordixon, 2017/05/22 21:29:01]

You're right. I changed that blindly without real intent.

 }
 
 ResourcePrefetchPredictorPageLoadMetricsObserver::
@@ -76,7 +79,7 @@ void ResourcePrefetchPredictorPageLoadMetricsObserver::
         const page_load_metrics::PageLoadExtraInfo& extra_info) {
   predictors::NavigationID navigation_id(web_contents_);
 
-  predictor_->RecordFirstContentfulPaint(
+  collector_->RecordFirstContentfulPaint(
       navigation_id, extra_info.navigation_start +
                          timing.paint_timing.first_contentful_paint.value());
   if (record_histograms_) {