Notify page load metrics when the app enters the background.

chrome/browser/page_load_metrics/metrics_web_contents_observer.cc

Index: chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
diff --git a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
index 4f1635151f42b52ef3e52a75ff967db51a72ba94..3f13df0ce8d73eb99779610a5b9f59252207edf1 100644
--- a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
+++ b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
@@ -53,6 +53,8 @@ const char kClientRedirectWithoutPaint[] =
     "PageLoad.Internal.ClientRedirect.NavigationWithoutPaint";
 const char kCommitToCompleteNoTimingIPCs[] =
     "PageLoad.Internal.CommitToComplete.NoTimingIPCs";
+const char kPageLoadCompletedAfterAppBackground[] =
+    "PageLoad.Internal.PageLoadCompleted.AfterAppBackground";
 
 }  // namespace internal
 
@@ -247,6 +249,7 @@ PageLoadTracker::PageLoadTracker(
     int aborted_chain_size,
     int aborted_chain_size_same_url)
     : did_stop_tracking_(false),
+      app_entered_background_(false),
       navigation_start_(navigation_handle->NavigationStart()),
       url_(navigation_handle->GetURL()),
       abort_type_(ABORT_NONE),
@@ -263,6 +266,10 @@ PageLoadTracker::PageLoadTracker(
 }
 
 PageLoadTracker::~PageLoadTracker() {
+  if (app_entered_background_) {
+    UMA_HISTOGRAM_BOOLEAN(internal::kPageLoadCompletedAfterAppBackground, true);

[Alexei Svitkine (slow), 2016/07/29 17:31:27]

Each histogram macro resolves to a lot of machine code.

To avoid the extra bloat, please make a helper function for logging this
histogram and call that.

[Bryan McQuade, 2016/07/29 17:48:10]

Ah, right, thanks for reminding me about this. Done, thanks!

+  }
+
   if (did_stop_tracking_)
     return;
 
@@ -398,6 +405,14 @@ void PageLoadTracker::OnInputEvent(const blink::WebInputEvent& event) {
   }
 }
 
+void PageLoadTracker::FlushMetricsOnAppEnterBackground() {
+  if (!app_entered_background_) {
+    UMA_HISTOGRAM_BOOLEAN(internal::kPageLoadCompletedAfterAppBackground,
+                          false);
+    app_entered_background_ = true;
+  }
+}
+
 void PageLoadTracker::NotifyClientRedirectTo(
     const PageLoadTracker& destination) {
   if (timing_.first_paint) {
@@ -805,6 +820,17 @@ void MetricsWebContentsObserver::OnInputEvent(
     committed_load_->OnInputEvent(event);
 }
 
+void MetricsWebContentsObserver::FlushMetricsOnAppEnterBackground() {
+  if (committed_load_)
+    committed_load_->FlushMetricsOnAppEnterBackground();
+  for (const auto& kv : provisional_loads_) {
+    kv.second->FlushMetricsOnAppEnterBackground();
+  }
+  for (const auto& tracker : aborted_provisional_loads_) {
+    tracker->FlushMetricsOnAppEnterBackground();
+  }
+}
+
 void MetricsWebContentsObserver::DidRedirectNavigation(
     content::NavigationHandle* navigation_handle) {
   if (!navigation_handle->IsInMainFrame())