[Sessions] Add detailed logging of SessionRestore events.

chrome/browser/sessions/session_restore.cc

Index: chrome/browser/sessions/session_restore.cc
diff --git a/chrome/browser/sessions/session_restore.cc b/chrome/browser/sessions/session_restore.cc
index 840219227c5bc0ea450d9c93b37108a94e77b5ac..07ac111def570b93c1f8e44420911f95f2125138 100644
--- a/chrome/browser/sessions/session_restore.cc
+++ b/chrome/browser/sessions/session_restore.cc
@@ -48,6 +48,7 @@
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
+#include "content/public/browser/session_restore_uma.h"
 #include "content/public/browser/session_storage_namespace.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/browser/web_contents.h"
@@ -181,6 +182,10 @@ class SessionRestoreImpl : public content::NotificationObserver {
     // Always create in a new window.
     FinishedTabCreation(true, true, created_contents);
 
+    // Record the number of tabs associated with this session restore.
+    UMA_HISTOGRAM_COUNTS_100(content::kSessionRestoreTabCount,

[sky, 2015/05/07 20:23:45]

Please try to keep all stats collection in SessionRestoreStatsCollector.

+                             created_contents.size());
+
     on_session_restored_callbacks_->Notify(
         static_cast<int>(created_contents.size()));
 
@@ -224,6 +229,10 @@ class SessionRestoreImpl : public content::NotificationObserver {
           tab.pinned, true, nullptr, tab.user_agent_override);
       // Start loading the tab immediately.
       web_contents->GetController().LoadIfNecessary();
+      UMA_HISTOGRAM_ENUMERATION(
+          content::kSessionRestoreTabActions,
+          content::kSessionRestoreTabActionsUma_ForegroundTabLoaded,
+          content::kSessionRestoreTabActionsUma_Max);
     }
 
     if (use_new_window) {
@@ -522,6 +531,10 @@ class SessionRestoreImpl : public content::NotificationObserver {
         restored_tab.contents = contents;
         restored_tab.is_active = is_selected_tab;
         created_contents->push_back(restored_tab);
+        UMA_HISTOGRAM_ENUMERATION(
+            content::kSessionRestoreTabActions,
+            content::kSessionRestoreTabActionsUma_TabCreated,
+            content::kSessionRestoreTabActionsUma_Max);
 
         // If this isn't the selected tab, there's nothing else to do.
         if (!is_selected_tab)
@@ -547,6 +560,10 @@ class SessionRestoreImpl : public content::NotificationObserver {
           restored_tab.contents = contents;
           restored_tab.is_active = false;
           created_contents->push_back(restored_tab);
+          UMA_HISTOGRAM_ENUMERATION(
+              content::kSessionRestoreTabActions,
+              content::kSessionRestoreTabActionsUma_TabCreated,
+              content::kSessionRestoreTabActionsUma_Max);
         }
       }
     }
@@ -721,6 +738,10 @@ Browser* SessionRestore::RestoreSession(
   chromeos::BootTimesRecorder::Get()->AddLoginTimeMarker(
       "SessionRestore-Start", false);
 #endif
+  UMA_HISTOGRAM_ENUMERATION(
+          content::kSessionRestoreActions,
+          content::kSessionRestoreActionsUma_Initiated,
+          content::kSessionRestoreActionsUma_Max);
   DCHECK(profile);
   // Always restore from the original profile (incognito profiles have no
   // session service).