Adding overview / layer framework to Activities so that unloaded / sleeping activities can be shown…

athena/content/app_activity_registry.cc

Index: athena/content/app_activity_registry.cc
diff --git a/athena/content/app_activity_registry.cc b/athena/content/app_activity_registry.cc
index 24505df40992550e3e2922d23ecc7de1512ee8a9..23ec42c7670e0f88e8c68088416a1f66149eb360 100644
--- a/athena/content/app_activity_registry.cc
+++ b/athena/content/app_activity_registry.cc
@@ -12,6 +12,10 @@
 #include "athena/resource_manager/public/resource_manager.h"
 #include "athena/wm/public/window_list_provider.h"
 #include "athena/wm/public/window_manager.h"
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
+#include "base/thread_task_runner_handle.h"
 #include "ui/aura/window.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
@@ -79,11 +83,11 @@ void AppActivityRegistry::Unload() {
   unloaded_activity_proxy_ = new AppActivityProxy(GetMruActivity(), this);
   ActivityManager::Get()->AddActivity(unloaded_activity_proxy_);
 
-  // Unload the application. This operation will be asynchronous.
-  if (!ExtensionsDelegate::Get(browser_context_)->UnloadApp(app_id_)) {
-    while(!activity_list_.empty())
-      Activity::Delete(activity_list_.back());
-  }
+  // Unload the application asynchronously to avoid the activity destruction
+  // while we are in an observerloop.

[sadrul, 2014/09/12 16:30:14]

I am not sure what this means, but if you mean while iterating over
ObserverList, then that should be fine (i.e. you can add/remove observers from
the ObserverList you are iterating over).

[Mr4D (OOO till 08-26), 2014/09/12 20:11:26]

Updated the comment.

But I do not remember exactly how I did get into this situation. (I think it was
a special case where the last item got erased) I will have another look into
this and let you know, but first lets land this patch (there is already far too
much addressed which is far from ideal).

+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::Bind(&AppActivityRegistry::DelayedUnload, base::Unretained(this)));
 }
 
 void AppActivityRegistry::ProxyDestroyed(AppActivityProxy* proxy) {
@@ -103,6 +107,13 @@ void AppActivityRegistry::RestartApplication(AppActivityProxy* proxy) {
   ExtensionsDelegate::Get(browser_context_)->LaunchApp(app_id_);
 }
 
+void AppActivityRegistry::DelayedUnload() {
+  if (!ExtensionsDelegate::Get(browser_context_)->UnloadApp(app_id_)) {
+    while(!activity_list_.empty())
+      Activity::Delete(activity_list_.back());
+  }
+}
+
 AppActivity* AppActivityRegistry::GetMruActivity() {
   DCHECK(activity_list_.size());
   WindowListProvider* window_list_provider =