predictors: Mark before_first_contentful_paint for resources fetched before fcp.

chrome/browser/predictors/resource_prefetch_predictor.cc

Index: chrome/browser/predictors/resource_prefetch_predictor.cc
diff --git a/chrome/browser/predictors/resource_prefetch_predictor.cc b/chrome/browser/predictors/resource_prefetch_predictor.cc
index 58d01b5df36a23eabb6ebf86be8c50d4a700047b..3ff92fe15c30be1cf49f8565f0c50573359aa7b0 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor.cc
+++ b/chrome/browser/predictors/resource_prefetch_predictor.cc
@@ -469,6 +469,8 @@ ResourcePrefetchPredictor::OriginRequestSummary::~OriginRequestSummary() {}
 ResourcePrefetchPredictor::URLRequestSummary::URLRequestSummary()
     : resource_type(content::RESOURCE_TYPE_LAST_TYPE),
       priority(net::IDLE),
+      response_time(base::TimeTicks()),
+      before_first_contentful_paint(false),
       was_cached(false),
       has_validators(false),
       always_revalidate(false),
@@ -490,6 +492,7 @@ bool ResourcePrefetchPredictor::URLRequestSummary::SummarizeResponse(
   if (!request_info)
     return false;
 
+  summary->response_time = base::TimeTicks::Now();
   summary->resource_url = request.original_url();
   summary->request_url = request.url();
   content::ResourceType resource_type_from_request =
@@ -517,7 +520,9 @@ bool ResourcePrefetchPredictor::URLRequestSummary::SummarizeResponse(
 
 ResourcePrefetchPredictor::PageRequestSummary::PageRequestSummary(
     const GURL& i_main_frame_url)
-    : main_frame_url(i_main_frame_url), initial_url(i_main_frame_url) {}
+    : main_frame_url(i_main_frame_url),
+      initial_url(i_main_frame_url),
+      first_contentful_paint(base::TimeTicks::Max()) {}
 
 ResourcePrefetchPredictor::PageRequestSummary::PageRequestSummary(
     const PageRequestSummary& other) = default;
@@ -645,6 +650,15 @@ void ResourcePrefetchPredictor::RecordMainFrameLoadComplete(
   }
 }
 
+void ResourcePrefetchPredictor::RecordFirstContentfulPaint(
+    const NavigationID& navigation_id,
+    const base::TimeTicks& first_contentful_paint) {

[alexilin, 2017/04/21 13:49:05]

Please add following lines to the beginning of the method:
  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  if (initialization_state_ != INITIALIZED)
    return;

[trevordixon, 2017/04/25 12:46:09]

Done.

+  NavigationMap::iterator nav_it = inflight_navigations_.find(navigation_id);
+  if (nav_it != inflight_navigations_.end()) {

[alexilin, 2017/04/21 13:49:05]

very tiny nit:
You could omit curly braces.

[trevordixon, 2017/04/25 12:46:09]

OK.

+    nav_it->second->first_contentful_paint = first_contentful_paint;
+  }
+}
+
 void ResourcePrefetchPredictor::StartPrefetching(const GURL& url,
                                                  PrefetchOrigin origin) {
   TRACE_EVENT1("browser", "ResourcePrefetchPredictor::StartPrefetching", "url",
@@ -844,6 +858,12 @@ void ResourcePrefetchPredictor::OnNavigationComplete(
   std::unique_ptr<PageRequestSummary> summary = std::move(nav_it->second);
   inflight_navigations_.erase(nav_it);
 
+  // Set before_first_contentful paint for each resource.
+  for (auto& request_summary : summary->subresource_requests) {
+    request_summary.before_first_contentful_paint =
+        request_summary.response_time < summary->first_contentful_paint;
+  }
+
   const GURL& initial_url = summary->initial_url;
   ResourcePrefetchPredictor::Prediction prediction;
   bool has_data = GetPrefetchData(initial_url, &prediction);
@@ -1419,6 +1439,8 @@ void ResourcePrefetchPredictor::LearnNavigation(
       resource_to_add->set_average_position(i + 1);
       resource_to_add->set_priority(
           static_cast<ResourceData::Priority>(summary.priority));
+      resource_to_add->set_before_first_contentful_paint(
+          summary.before_first_contentful_paint);
       resource_to_add->set_has_validators(new_resources[i].has_validators);
       resource_to_add->set_always_revalidate(
           new_resources[i].always_revalidate);