Ports SystemModalContainerLayoutManager to ash/common

ash/aura/wm_window_aura.cc

Index: ash/aura/wm_window_aura.cc
diff --git a/ash/aura/wm_window_aura.cc b/ash/aura/wm_window_aura.cc
index e4c6b75a7a16d072a3542d81c1f9c50559a9a3db..f7dfea0c6efacaeca171195b76039f428e59c20a 100644
--- a/ash/aura/wm_window_aura.cc
+++ b/ash/aura/wm_window_aura.cc
@@ -291,6 +291,9 @@ int WmWindowAura::GetIntProperty(WmWindowProperty key) {
   if (key == WmWindowProperty::TOP_VIEW_INSET)
     return window_->GetProperty(aura::client::kTopViewInset);
 
+  if (key == WmWindowProperty::MODAL_TYPE)
+    return window_->GetProperty(aura::client::kModalKey);
+
   NOTREACHED();
   return 0;
 }
@@ -789,6 +792,8 @@ void WmWindowAura::OnWindowPropertyChanged(aura::Window* window,
     wm_property = WmWindowProperty::TOP_VIEW_INSET;
   } else if (key == aura::client::kExcludeFromMruKey) {
     wm_property = WmWindowProperty::EXCLUDE_FROM_MRU;
+  } else if (key == aura::client::kModalKey) {
+    wm_property = WmWindowProperty::MODAL_TYPE;

[James Cook, 2016/09/12 19:24:28]

optional: You could sort all these ifs() too, which would make it slightly
easier to see that you're not missing a case.

[sky, 2016/09/12 20:46:54]

Done.

   } else {
     return;
   }