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

chrome/browser/resource_coordinator/tab_manager_unittest.cc

Index: chrome/browser/resource_coordinator/tab_manager_unittest.cc
diff --git a/chrome/browser/resource_coordinator/tab_manager_unittest.cc b/chrome/browser/resource_coordinator/tab_manager_unittest.cc
index 60a00d2db21cae7479d83efe0eea664c8c3112bf..bb6e279bab72db94b4d21e0fb5ba78662059f092 100644
--- a/chrome/browser/resource_coordinator/tab_manager_unittest.cc
+++ b/chrome/browser/resource_coordinator/tab_manager_unittest.cc
@@ -17,9 +17,11 @@
 #include "base/test/simple_test_tick_clock.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
+#include "chrome/browser/browser_process.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/resource_coordinator/tab_manager_web_contents_data.h"
 #include "chrome/browser/resource_coordinator/tab_stats.h"
+#include "chrome/browser/sessions/tab_loader.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/tabs/test_tab_strip_model_delegate.h"
 #include "chrome/common/chrome_features.h"
@@ -492,4 +494,23 @@ TEST_F(TabManagerTest, ActivateTabResetPurgeState) {
   EXPECT_FALSE(tab_manager.GetWebContentsData(tab2)->is_purged());
 }
 
+TEST_F(TabManagerTest, OnSessionRestoreStartedAndEnded) {
+  content::WebContents* test_contents =
+      WebContentsTester::CreateTestWebContents(browser_context(), nullptr);
+
+  std::vector<SessionRestoreDelegate::RestoredTab> restored_tabs{
+      SessionRestoreDelegate::RestoredTab(test_contents, true, false, false)};
+
+  TabManager* tab_manager = g_browser_process->GetTabManager();
+  EXPECT_FALSE(tab_manager->IsInSessionRestore());
+
+  TabLoader::RestoreTabs(restored_tabs, base::TimeTicks());
+  EXPECT_TRUE(tab_manager->IsInSessionRestore());
+
+  WebContentsTester::For(test_contents)->NavigateAndCommit(GURL("about:blank"));
+  WebContentsTester::For(test_contents)->TestSetIsLoading(false);
+  // Session restore ends when all restored tabs finish loading
+  EXPECT_FALSE(tab_manager->IsInSessionRestore());
+}
+
 }  // namespace resource_coordinator