[Tab Metrics] Measure FP, FCP and FMP for Foreground Tab during Session Restore

chrome/browser/page_load_metrics/page_load_metrics_initialize.cc

 // Copyright 2015 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.
 
 #include "chrome/browser/page_load_metrics/page_load_metrics_initialize.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/macros.h"
@@ skipping 16 matching lines @@
 #include "chrome/browser/page_load_metrics/observers/https_engagement_metrics/https_engagement_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/loading_predictor_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/lofi_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/media_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/omnibox_suggestion_used_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/prerender_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/protocol_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.h"
+#include "chrome/browser/page_load_metrics/observers/session_restore_foreground_tab_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/tab_restore_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_embedder_interface.h"
 #include "chrome/browser/page_load_metrics/page_load_tracker.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search/search.h"
 #include "components/rappor/rappor_service_impl.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 75 matching lines @@
 #if defined(OS_ANDROID)
     tracker->AddObserver(
         base::MakeUnique<AndroidPageLoadMetricsObserver>(web_contents_));
 #endif  // OS_ANDROID
     std::unique_ptr<page_load_metrics::PageLoadMetricsObserver>
         loading_predictor_observer =
             LoadingPredictorPageLoadMetricsObserver::CreateIfNeeded(
                 web_contents_);
     if (loading_predictor_observer)
       tracker->AddObserver(std::move(loading_predictor_observer));
+#if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX)

[chrisha, 2017/06/15 19:44:56]

OS_CHROMEOS as well?

[ducbui, 2017/06/15 23:27:46]

TabManager seems not supported on CHROMEOS.
BrowserProcessImpl::GetTabManager() returns non-null only if 
defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX)
(https://cs.chromium.org/chromium/src/chrome/browser/browser_process_impl.cc?l...)

Does OS_LINUX include OS_CHROMEOS?

[chrisha, 2017/06/16 16:52:35]

It is supported on ChromeOS, so yes I suppose OS_LINUX must subsume OS_CHROMEOS.

I dislike the fragility of replicating the #ifdef logic here as well. Can we
make the code compile on all platforms and make CreateIfNeeded return null when
not necessary?

[ducbui, 2017/06/16 20:59:55]

That's a good point. I would remove the #if and make CreateIfNeeded() return
null when TabManager is not supported (i.e., BrowserProcess::GetTabManager()
returns null).

+    std::unique_ptr<page_load_metrics::PageLoadMetricsObserver>
+        session_restore_foreground_tab_observer =
+            SessionRestoreForegroundTabPageLoadMetricsObserver::
+                CreateIfNeeded();
+    if (session_restore_foreground_tab_observer)
+      tracker->AddObserver(std::move(session_restore_foreground_tab_observer));
+#endif
   } else {
     std::unique_ptr<page_load_metrics::PageLoadMetricsObserver>
         prerender_observer =
             PrerenderPageLoadMetricsObserver::CreateIfNeeded(web_contents_);
     if (prerender_observer)
       tracker->AddObserver(std::move(prerender_observer));
   }
   tracker->AddObserver(
       base::MakeUnique<OmniboxSuggestionUsedMetricsObserver>(IsPrerendering()));
   tracker->AddObserver(
@@ skipping 21 matching lines @@
 
 void InitializePageLoadMetricsForWebContents(
     content::WebContents* web_contents,
     const base::Optional<content::WebContents::CreateParams>& create_params) {
   page_load_metrics::MetricsWebContentsObserver::CreateForWebContents(
       web_contents, create_params,
       base::MakeUnique<PageLoadMetricsEmbedder>(web_contents));
 }
 
 }  // namespace chrome