[TabMetrics] Add signals that mark the start and end of session restore.

chrome/browser/sessions/tab_loader.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/sessions/tab_loader.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/memory/memory_coordinator_client_registry.h"
 #include "base/memory/memory_coordinator_proxy.h"
 #include "base/memory/memory_pressure_monitor.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "build/build_config.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/resource_coordinator/tab_manager.h"
 #include "chrome/browser/sessions/session_restore_stats_collector.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "components/favicon/content/content_favicon_driver.h"
 #include "components/variations/variations_associated_data.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_widget_host.h"
@@ skipping 70 matching lines @@
       loading_enabled_(true),
       started_to_load_count_(0),
       restore_started_(restore_started) {
   stats_collector_ = new SessionRestoreStatsCollector(
       restore_started,
       base::MakeUnique<
           SessionRestoreStatsCollector::UmaStatsReportingDelegate>());
   shared_tab_loader_ = this;
   this_retainer_ = this;
   base::MemoryCoordinatorClientRegistry::GetInstance()->Register(this);
+  MarkSessionRestoreStarted();
 }
 
 TabLoader::~TabLoader() {
   DCHECK(tabs_loading_.empty() && tabs_to_load_.empty());
   DCHECK(shared_tab_loader_ == this);
   shared_tab_loader_ = nullptr;
   base::MemoryCoordinatorClientRegistry::GetInstance()->Unregister(this);
+  MarkSessionRestoreEnded();
 }
 
 void TabLoader::StartLoading(const std::vector<RestoredTab>& tabs) {
   // Add the tabs to the list of tabs loading/to load and register them for
   // notifications. Also, restore the favicons of the background tabs (the title
   // has already been set by now).This avoids having blank icons in case the
   // restore is halted due to memory pressure. Also, when multiple tabs are
   // restored to a single window, the title may not appear, and the user will
   // have no way of finding out which tabs corresponds to which page if the icon
   // is a generic grey one.
@@ skipping 184 matching lines @@
     // Notify the stats collector that a tab's loading has been deferred due to
     // memory pressure.
     stats_collector_->DeferTab(tab);
   }
   // By calling |LoadNextTab| explicitly, we make sure that the
   // |NOTIFICATION_SESSION_RESTORE_DONE| event gets sent.
   LoadNextTab();
 }
 
 // static
+void TabLoader::MarkSessionRestoreStarted() {
+  resource_coordinator::TabManager* tab_manager =
+      g_browser_process->GetTabManager();
+  if (tab_manager)

[fmeawad, 2017/06/14 15:34:58]

Can this be a DCHECK instead?
Similar to here maybe:
https://cs.chromium.org/chromium/src/chrome/browser/memory/chrome_memory_coor...
#if !defined(OS_ANDROID)

[fmeawad, 2017/06/14 16:20:56]

This is why we put the DCHECK, if the check is always true, it should not be
there.

[ducbui, 2017/06/14 16:24:18]

Is the usage of TabLoader limited to only tab-manager-supported platforms?

[ducbui, 2017/06/14 16:47:39]

The TabLoader is not compiled on Android and on ChromeCast because session
service is not enabled on these platforms.
https://cs.chromium.org/chromium/src/chrome/browser/BUILD.gn?type=cs&q=enable...
https://cs.chromium.org/chromium/src/chrome/common/features.gni?type=cs&q=ENA...

Therefore, I will change the if (tab_manager) to a DCHECK.

+    tab_manager->MarkSessionRestoreStarted();
+}
+
+// static
+void TabLoader::MarkSessionRestoreEnded() {
+  resource_coordinator::TabManager* tab_manager =
+      g_browser_process->GetTabManager();
+  if (tab_manager)
+    tab_manager->MarkSessionRestoreEnded();
+}
+
+// static
 TabLoader* TabLoader::shared_tab_loader_ = nullptr;