[Session restore] Add DontRestoreBackgroundTabs group to collect stats.

BUG=

Review URL: https://codereview.chromium.org/1137033004

Cr-Commit-Position: refs/heads/master@{#329245}

chrome/browser/sessions/session_restore_delegate.cc

@@ -8,6 +8,7 @@
 #include "chrome/browser/sessions/session_restore_stats_collector.h"
 #include "chrome/browser/sessions/tab_loader.h"
 #include "chrome/common/url_constants.h"
+#include "components/favicon/content/content_favicon_driver.h"
 #include "content/public/browser/web_contents.h"
 
 namespace {
@@ -64,6 +65,23 @@ bool SessionRestoreDelegate::RestoredTab::operator<(
 void SessionRestoreDelegate::RestoreTabs(
     const std::vector<RestoredTab>& tabs,
     const base::TimeTicks& restore_started) {
-  SessionRestoreStatsCollector::TrackTabs(tabs, restore_started);
-  TabLoader::RestoreTabs(tabs, restore_started);
+  // This experiment allows us to have comparative numbers for session restore
+  // metrics. It will be removed once those numbers are obtained.
+  // TODO(georgesak): Remove this experiment when stats are collected.
+  base::FieldTrial* trial =
+      base::FieldTrialList::Find("IntelligentSessionRestore");
+  if (!trial || trial->group_name() != "DontRestoreBackgroundTabs") {
+    SessionRestoreStatsCollector::TrackTabs(tabs, restore_started);
+    TabLoader::RestoreTabs(tabs, restore_started);
+  } else {
+    SessionRestoreStatsCollector::TrackActiveTabs(tabs, restore_started);
+    for (auto& restored_tab : tabs) {
+      if (!restored_tab.is_active()) {
+        favicon::ContentFaviconDriver* favicon_driver =
+            favicon::ContentFaviconDriver::FromWebContents(
+                restored_tab.contents());
+        favicon_driver->FetchFavicon(favicon_driver->GetActiveURL());
+      }
+    }
+  }
 }

chrome/browser/sessions/session_restore_stats_collector.cc

@@ -27,6 +27,21 @@ void SessionRestoreStatsCollector::TrackTabs(
   shared_collector_->AddTabs(tabs);
 }
 
+// static
+void SessionRestoreStatsCollector::TrackActiveTabs(
+    const std::vector<SessionRestoreDelegate::RestoredTab>& tabs,
+    const base::TimeTicks& restore_started) {
+  if (!shared_collector_)
+    shared_collector_ = new SessionRestoreStatsCollector(restore_started);
+
+  std::vector<SessionRestoreDelegate::RestoredTab> active_tabs;
+  for (auto tab : tabs) {
+    if (tab.is_active())
+      active_tabs.push_back(tab);
+  }
+  shared_collector_->AddTabs(active_tabs);
+}
+
 SessionRestoreStatsCollector::SessionRestoreStatsCollector(
     const base::TimeTicks& restore_started)
     : got_first_foreground_load_(false),

chrome/browser/sessions/session_restore_stats_collector.h

@@ -30,6 +30,12 @@ class SessionRestoreStatsCollector
       const std::vector<SessionRestoreDelegate::RestoredTab>& tabs,
       const base::TimeTicks& restore_started);
 
+  // Called to start tracking only active tabs. If a restore is already
+  // occuring, the tabs are added to the existing list of tracked tabs.
+  static void TrackActiveTabs(
+      const std::vector<SessionRestoreDelegate::RestoredTab>& tabs,
+      const base::TimeTicks& restore_started);
+
  private:
   friend class base::RefCounted<SessionRestoreStatsCollector>;