[Session restore] Add MRU logic to loading of background pages.

components/sessions/session_service_commands.cc

Index: components/sessions/session_service_commands.cc
diff --git a/components/sessions/session_service_commands.cc b/components/sessions/session_service_commands.cc
index eca2b4d718186d97d38fa77917213f3cb6cd34ac..f2bb9ea869913a7ac4eb7dd1fc05e9c62c7fc3ff 100644
--- a/components/sessions/session_service_commands.cc
+++ b/components/sessions/session_service_commands.cc
@@ -38,6 +38,7 @@ static const SessionCommand::id_type kCommandWindowClosed = 17;
 static const SessionCommand::id_type kCommandSetTabUserAgentOverride = 18;
 static const SessionCommand::id_type kCommandSessionStorageAssociated = 19;
 static const SessionCommand::id_type kCommandSetActiveWindow = 20;
+static const SessionCommand::id_type kCommandActivationTime = 21;
 
 namespace {
 
@@ -89,6 +90,11 @@ struct PinnedStatePayload {
   bool pinned_state;
 };
 
+struct ActivationTimePayload {
+  SessionID::id_type tab_id;
+  int64 last_activation_time;
+};
+
 // Persisted versions of ui::WindowShowState that are written to disk and can
 // never change.
 enum PersistedWindowShowState {
@@ -558,6 +564,18 @@ bool CreateTabsAndWindows(const ScopedVector<SessionCommand>& data,
         break;
       }
 
+      case kCommandActivationTime: {
+        ActivationTimePayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload))) {
+          DVLOG(1) << "Failed reading command " << command->id();
+          return true;
+        }
+        SessionTab* tab = GetTab(payload.tab_id, tabs);
+        tab->last_activation_time =
+            base::TimeTicks::FromInternalValue(payload.last_activation_time);
+        break;
+      }
+
       default:
         // TODO(skuhne): This might call back into a callback handler to extend
         // the command set for specific implementations.
@@ -704,6 +722,18 @@ scoped_ptr<SessionCommand> CreateSetActiveWindowCommand(
   return command;
 }
 
+scoped_ptr<SessionCommand> CreateActivationTimeCommand(
+    const SessionID& tab_id,
+    base::TimeTicks activation_time) {
+  ActivationTimePayload payload = {0};
+  payload.tab_id = tab_id.id();
+  payload.last_activation_time = activation_time.ToInternalValue();
+  scoped_ptr<SessionCommand> command(
+      new SessionCommand(kCommandActivationTime, sizeof(payload)));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
 scoped_ptr<SessionCommand> CreateTabNavigationPathPrunedFromBackCommand(
     const SessionID& tab_id,
     int count) {