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

athena/content/app_activity.cc

Index: athena/content/app_activity.cc
diff --git a/athena/content/app_activity.cc b/athena/content/app_activity.cc
index b8b1c5fa22037a7bf7134f70ef64d48a3ba723f0..cef358e043e2e6f417c66c2bbecaa2308016b569 100644
--- a/athena/content/app_activity.cc
+++ b/athena/content/app_activity.cc
@@ -78,7 +78,7 @@ void AppActivity::SetCurrentState(Activity::ActivityState state) {
 }
 
 Activity::ActivityState AppActivity::GetCurrentState() {
-  DCHECK(web_view_ || ACTIVITY_UNLOADED == current_state_);
+  DCHECK(GetContentsView() || ACTIVITY_UNLOADED == current_state_);
   return current_state_;
 }
 
@@ -95,9 +95,9 @@ Activity::ActivityMediaState AppActivity::GetMediaState() {
 }
 
 aura::Window* AppActivity::GetWindow() {
-  return web_view_ && web_view_->GetWidget()
-             ? web_view_->GetWidget()->GetNativeWindow()
-             : nullptr;
+  views::View* view = GetContentsView();
+  return (view && view->GetWidget()) ? view->GetWidget()->GetNativeWindow()
+                                     : nullptr;
 }
 
 content::WebContents* AppActivity::GetWebContents() {
@@ -161,7 +161,7 @@ SkColor AppActivity::GetRepresentativeColor() const {
 }
 
 base::string16 AppActivity::GetTitle() const {
-  return web_view_->GetWebContents()->GetTitle();
+  return web_view_ ? web_view_->GetWebContents()->GetTitle() : base::string16();
 }
 
 gfx::ImageSkia AppActivity::GetIcon() const {
@@ -233,11 +233,12 @@ void AppActivity::DidUpdateFaviconURL(
 // Note: This should only get called once for an |app_window| of the
 // |activity|.
 void AppActivity::RegisterActivity() {
-  content::WebContents* web_contents = web_view_->GetWebContents();
+  content::WebContents* web_contents = web_view_ ? web_view_->GetWebContents()
+                                                 : nullptr;
   AppRegistry* app_registry = AppRegistry::Get();
   // Get the application's registry.
   app_activity_registry_ = app_registry->GetAppActivityRegistry(
-      app_id_, web_contents->GetBrowserContext());
+      app_id_, web_contents ? web_contents->GetBrowserContext() : nullptr);
   DCHECK(app_activity_registry_);
   // Register the activity.
   app_activity_registry_->RegisterAppActivity(this);