Support creation of toplevel mus::Windows on separate displays

ash/common/wm/container_finder.cc

Index: ash/common/wm/container_finder.cc
diff --git a/ash/common/wm/container_finder.cc b/ash/common/wm/container_finder.cc
index 60785c75c48e6905f1864cd6f62024c417d1d9e5..f9ce52ead559d402bbb14335f2ca67f89a5959c1 100644
--- a/ash/common/wm/container_finder.cc
+++ b/ash/common/wm/container_finder.cc
@@ -76,7 +76,9 @@ WmWindow* GetDefaultParent(WmWindow* context,
     // Transient window should use the same root as its transient parent.
     target_root = transient_parent->GetRootWindow();
   } else {
-    target_root = FindContainerRoot(context->GetShell(), bounds);
+    target_root = context->GetRootWindow();

[mfomitchev, 2016/11/15 20:29:34]

This makes sense to me, but the original way seems like it should work too.
Perhaps we need to fix FindContainerRoot?

[thanhph, 2016/11/15 21:09:55]

If the bounds is correct, then this function FindContainerRoot is probably doing
a right thing. I think I passed in the incorrect bounds during my test case
setup or this needs to be fixed in here

https://cs.chromium.org/chromium/src/ash/mus/root_window_controller.cc?type=c...

This current patch, however, uses the context to find root window so the
incorrect bounds don't affect the root window selection (unit test correctly
passed with this fix).

+    if (!target_root)
+      target_root = FindContainerRoot(context->GetShell(), bounds);
   }
 
   switch (window->GetType()) {