Revert 188217 "Switch Windows to use the MessagePopupCollection"

ui/message_center/views/message_popup_collection.cc

Index: ui/message_center/views/message_popup_collection.cc
===================================================================
--- ui/message_center/views/message_popup_collection.cc	(revision 188316)
+++ ui/message_center/views/message_popup_collection.cc	(working copy)
@@ -47,10 +47,7 @@
     views::Widget::InitParams params(
         views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
     params.keep_on_top = true;
-    if (context)
-      params.context = context;
-    else
-      params.top_level = true;
+    params.context = context;
     params.transparent = true;
     // The origin of the initial bounds are set to (0, 0). It'll then moved by
     // MessagePopupCollection.
@@ -149,17 +146,8 @@
     return;
   }
 
-  gfx::Rect work_area;
-  if (!context_) {
-    // On Win+Aura, we don't have a context since the popups currently show up
-    // on the Windows desktop, not in the Aura/Ash desktop.  This code will
-    // display the popups on the primary display.
-    gfx::Screen* screen = gfx::Screen::GetNativeScreen();
-    work_area = screen->GetPrimaryDisplay().work_area();
-  } else {
-    gfx::Screen* screen = gfx::Screen::GetScreenFor(context_);
-    work_area = screen->GetDisplayNearestWindow(context_).work_area();
-  }
+  gfx::Screen* screen = gfx::Screen::GetScreenFor(context_);
+  gfx::Rect work_area = screen->GetDisplayNearestWindow(context_).work_area();
 
   std::set<std::string> old_toast_ids;
   for (ToastContainer::iterator iter = toasts_.begin(); iter != toasts_.end();