[DO NOT COMMIT] Re-use the dafsa code for s-w-r histograms

components/page_load_metrics/browser/metrics_web_contents_observer.cc

Index: components/page_load_metrics/browser/metrics_web_contents_observer.cc
diff --git a/components/page_load_metrics/browser/metrics_web_contents_observer.cc b/components/page_load_metrics/browser/metrics_web_contents_observer.cc
index 2961f1ecb5dd766e48da0cd1dc87bd6f8ba53cb7..71ceebcac1fc9d20014fb3868780ce7ccd31ed16 100644
--- a/components/page_load_metrics/browser/metrics_web_contents_observer.cc
+++ b/components/page_load_metrics/browser/metrics_web_contents_observer.cc
@@ -17,6 +17,8 @@
 #include "content/public/browser/web_contents_user_data.h"
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_message_macros.h"
+#include "net/base/swr_histogram_domains/swr_histogram_domains.h"
+#include "url/gurl.h"
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(
     page_load_metrics::MetricsWebContentsObserver);
@@ -64,7 +66,9 @@ base::Time WallTimeFromTimeTicks(base::TimeTicks time) {
                              base::TimeDelta::FromMinutes(10), 100)
 
 PageLoadTracker::PageLoadTracker(bool in_foreground)
-    : has_commit_(false), started_in_foreground_(in_foreground) {
+    : has_commit_(false),
+      started_in_foreground_(in_foreground),
+      include_in_stale_while_revalidate_experiment_(false) {
   RecordEvent(PAGE_LOAD_STARTED);
 }
 
@@ -89,6 +93,10 @@ void PageLoadTracker::Commit() {
   has_commit_ = true;
 }
 
+void PageLoadTracker::IncludeInStaleWhileRevalidateExperiment() {
+  include_in_stale_while_revalidate_experiment_ = true;

[Bryan McQuade, 2015/10/19 12:58:16]

just FYI (happened to find this CL): we don't want MetricsWebContentsObserver to
become a home for code for all the variants of things people want to track
related to page load metrics. That will quickly make the class unmanageable as
different teams add their logic. See page_load_histograms.cc for an example of
what we don't want to turn into. :)

Instead, if you want to log things related to page load metrics, we'd like to
add an observer interface to MetricsWebContentsObserver (maybe
PageLoadMetricsObserver) that provides you with the hooks you need to keep track
of and log metrics that your team needs.

Please reach out to csharrison@ to discuss what that API might look like. I
believe we should be able to prioritize that work to allow you to keep this
moving forward in a way that doesn't complicate the core
MetricsWebContentsObserver implementation.

[Adam Rice, 2015/10/19 13:34:44]

SGTM.

+}
+
 bool PageLoadTracker::UpdateTiming(const PageLoadTiming& timing) {
   // Throw away IPCs that are not relevant to the current navigation.
   if (!timing_.navigation_start.is_null() &&
@@ -134,6 +142,12 @@ void PageLoadTracker::RecordTimingHistograms() {
       PAGE_LOAD_HISTOGRAM("PageLoad.Timing2.NavigationToLoadEventFired.BG",
                           timing_.load_event_start);
     }
+    if (include_in_stale_while_revalidate_experiment_) {
+      PAGE_LOAD_HISTOGRAM(

[tyoshino (SeeGerritForStatus), 2015/10/30 07:48:02]

no need to align with the grouping above? bg or not bg

[Adam Rice, 2015/11/02 13:53:54]

When I tested manually, the BG or not BG distinction didn't work how I would
intuitively expect. For example, navigations across domains within a tab are
considered to start in the background.

So I decided it was best just to ignore the distinction and log everything.

[Bryan McQuade, 2015/11/02 14:22:39]

That seems like a bug. Can you open a bug with your findings assigned to
csharrison and cc me?

+          "PageLoad.Timing2.NavigationToLoadEventFired_"
+          "StaleWhileRevalidateExperiment",
+          timing_.load_event_start);
+    }
   }
   if (!timing_.first_layout.is_zero()) {
     if (timing_.first_layout < background_delta) {
@@ -145,6 +159,12 @@ void PageLoadTracker::RecordTimingHistograms() {
                           timing_.first_layout);
       RecordEvent(PAGE_LOAD_SUCCESSFUL_FIRST_LAYOUT_BACKGROUND);
     }
+    if (include_in_stale_while_revalidate_experiment_) {
+      PAGE_LOAD_HISTOGRAM(
+          "PageLoad.Timing2.NavigationToFirstLayout_"
+          "StaleWhileRevalidateExperiment",
+          timing_.first_layout);
+    }
   }
   if (!timing_.first_text_paint.is_zero()) {
     if (timing_.first_text_paint < background_delta) {
@@ -154,6 +174,12 @@ void PageLoadTracker::RecordTimingHistograms() {
       PAGE_LOAD_HISTOGRAM("PageLoad.Timing2.NavigationToFirstTextPaint.BG",
                           timing_.first_text_paint);
     }
+    if (include_in_stale_while_revalidate_experiment_) {
+      PAGE_LOAD_HISTOGRAM(
+          "PageLoad.Timing2.NavigationToFirstTextPaint_"
+          "StaleWhileRevalidateExperiment",
+          timing_.first_text_paint);
+    }
   }
 }
 
@@ -222,6 +248,11 @@ void MetricsWebContentsObserver::DidFinishNavigation(
   if (!IsRelevantNavigation(navigation_handle))
     return;
 
+  if (net::swr_histogram_domains::IsHostInSWRHistogramDomain(
+          navigation_handle->GetURL().host())) {
+    finished_nav->IncludeInStaleWhileRevalidateExperiment();
+  }
+
   committed_load_ = finished_nav.Pass();
   committed_load_->Commit();
 }