Desktop aura: Break aura::Window::SetParent in two.

ash/wm/workspace/workspace_window_resizer_unittest.cc

Index: ash/wm/workspace/workspace_window_resizer_unittest.cc
diff --git a/ash/wm/workspace/workspace_window_resizer_unittest.cc b/ash/wm/workspace/workspace_window_resizer_unittest.cc
index d8570ee6d471c6410f03d63e49e64bf831fe32c0..02d0b157968a38cae2e47926e627fadead38c3af 100644
--- a/ash/wm/workspace/workspace_window_resizer_unittest.cc
+++ b/ash/wm/workspace/workspace_window_resizer_unittest.cc
@@ -83,19 +83,19 @@ class WorkspaceWindowResizerTest : public test::AshTestBase {
     window_.reset(new aura::Window(&delegate_));
     window_->SetType(aura::client::WINDOW_TYPE_NORMAL);
     window_->Init(ui::LAYER_NOT_DRAWN);
-    window_->SetParent(NULL);
+    SetDefaultParentByPrimaryRootWindow(window_.get());
     window_->set_id(1);
 
     window2_.reset(new aura::Window(&delegate2_));
     window2_->SetType(aura::client::WINDOW_TYPE_NORMAL);
     window2_->Init(ui::LAYER_NOT_DRAWN);
-    window2_->SetParent(NULL);
+    SetDefaultParentByPrimaryRootWindow(window2_.get());
     window2_->set_id(2);
 
     window3_.reset(new aura::Window(&delegate3_));
     window3_->SetType(aura::client::WINDOW_TYPE_NORMAL);
     window3_->Init(ui::LAYER_NOT_DRAWN);
-    window3_->SetParent(NULL);
+    SetDefaultParentByPrimaryRootWindow(window3_.get());
     window3_->set_id(3);
   }