athena: Use ActivityList where appropriate, and fix AppActivity tests.

athena/activity/activity_manager_impl.cc

Index: athena/activity/activity_manager_impl.cc
diff --git a/athena/activity/activity_manager_impl.cc b/athena/activity/activity_manager_impl.cc
index a9981556d7f65dfc60e35944efe99fd01790b9e5..210c83b11301960ef6a992e3b4a5215c9a192ae5 100644
--- a/athena/activity/activity_manager_impl.cc
+++ b/athena/activity/activity_manager_impl.cc
@@ -69,27 +69,29 @@ void ActivityManagerImpl::AddActivity(Activity* activity) {
   CHECK(activities_.end() ==
         std::find(activities_.begin(), activities_.end(), activity));
   activities_.insert(activities_.begin(), activity);
-  views::Widget* widget = CreateWidget(activity);
-  widget->GetNativeView()->AddObserver(this);
-  activity->GetActivityViewModel()->Init();
-
-  FOR_EACH_OBSERVER(ActivityManagerObserver,
-                    observers_,
-                    OnActivityStarted(activity));
+  InitializeActivity(activity);
 }
 
 void ActivityManagerImpl::RemoveActivity(Activity* activity) {
   std::vector<Activity*>::iterator find =
       std::find(activities_.begin(), activities_.end(), activity);
-  DCHECK(find != activities_.end());
-  if (find != activities_.end()) {
-    FOR_EACH_OBSERVER(
-        ActivityManagerObserver, observers_, OnActivityEnding(activity));
-    activities_.erase(find);
-    views::Widget* widget = GetWidget(activity);
-    widget->GetNativeView()->RemoveObserver(this);
-    widget->Close();
-  }
+  if (find == activities_.end())
+    return;
+  activities_.erase(find);
+  UninitializeActivity(activity);
+}
+
+ScopedActivity ActivityManagerImpl::ReplaceActivity(Activity* to_replace,
+                                                    Activity* replace_with) {
+  std::vector<Activity*>::iterator find =
+      std::find(activities_.begin(), activities_.end(), to_replace);
+  if (find == activities_.end())
+    return ScopedActivity();
+  std::replace(find, find + 1, to_replace, replace_with);
+
+  UninitializeActivity(to_replace);
+  InitializeActivity(replace_with);
+  return ScopedActivity(to_replace);
 }
 
 const ActivityList& ActivityManagerImpl::GetActivityList() {
@@ -117,6 +119,23 @@ void ActivityManagerImpl::RemoveObserver(ActivityManagerObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+void ActivityManagerImpl::InitializeActivity(Activity* activity) {
+  views::Widget* widget = CreateWidget(activity);
+  widget->GetNativeView()->AddObserver(this);
+  activity->GetActivityViewModel()->Init();
+  FOR_EACH_OBSERVER(ActivityManagerObserver,
+                    observers_,
+                    OnActivityStarted(activity));
+}
+
+void ActivityManagerImpl::UninitializeActivity(Activity* activity) {
+  FOR_EACH_OBSERVER(
+      ActivityManagerObserver, observers_, OnActivityEnding(activity));
+  views::Widget* widget = GetWidget(activity);
+  widget->GetNativeView()->RemoveObserver(this);
+  widget->Close();
+}
+
 void ActivityManagerImpl::OnWindowDestroying(aura::Window* window) {
   Activity* activity = GetActivityForWindow(window);
   if (activity) {