Eliminate Shell::RootWindowList in favor of aura::Window::Windows.

ash/wm/workspace/workspace_layout_manager_unittest.cc

Index: ash/wm/workspace/workspace_layout_manager_unittest.cc
diff --git a/ash/wm/workspace/workspace_layout_manager_unittest.cc b/ash/wm/workspace/workspace_layout_manager_unittest.cc
index 1963b9b8e47570d457bee4c87d461e4bb16b12f8..4302f1dc44f9bdb6093f59bc2a286b2d743ff77a 100644
--- a/ash/wm/workspace/workspace_layout_manager_unittest.cc
+++ b/ash/wm/workspace/workspace_layout_manager_unittest.cc
@@ -97,7 +97,7 @@ TEST_F(WorkspaceLayoutManagerTest, KeepMinimumVisibilityInDisplays) {
     return;
 
   UpdateDisplay("300x400,400x500");
-  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+  aura::Window::Windows root_windows = Shell::GetAllRootWindows();
 
   DisplayLayout layout(DisplayLayout::TOP, 0);
   Shell::GetInstance()->display_manager()->
@@ -160,7 +160,7 @@ TEST_F(WorkspaceLayoutManagerTest, MaximizeInDisplayToBeRestored) {
     return;
   UpdateDisplay("300x400,400x500");
 
-  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+  aura::Window::Windows root_windows = Shell::GetAllRootWindows();
 
   scoped_ptr<aura::Window> window(
       CreateTestWindowInShellWithBounds(gfx::Rect(1, 2, 30, 40)));
@@ -210,7 +210,7 @@ TEST_F(WorkspaceLayoutManagerTest, FullscreenInDisplayToBeRestored) {
     return;
   UpdateDisplay("300x400,400x500");
 
-  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+  aura::Window::Windows root_windows = Shell::GetAllRootWindows();
 
   scoped_ptr<aura::Window> window(
       CreateTestWindowInShellWithBounds(gfx::Rect(1, 2, 30, 40)));