fix shelf color with modal dialog.

ash/wm/workspace_controller.cc

Index: ash/wm/workspace_controller.cc
diff --git a/ash/wm/workspace_controller.cc b/ash/wm/workspace_controller.cc
index fd34e8f39af3548740c908d3d4770e9b249ae1f5..e127c8d5653fd66002d8f535a9cc7a656fab34fe 100644
--- a/ash/wm/workspace_controller.cc
+++ b/ash/wm/workspace_controller.cc
@@ -63,7 +63,8 @@ wm::WorkspaceWindowState WorkspaceController::GetWindowState() const {
 
   const gfx::Rect shelf_bounds(Shelf::ForWindow(viewport_)->GetIdealBounds());
   bool window_overlaps_launcher = false;
-  auto mru_list = Shell::Get()->mru_window_tracker()->BuildMruWindowList();
+  auto mru_list =
+      Shell::Get()->mru_window_tracker()->BuildWindowListIgnoreModal();
 
   for (aura::Window* window : mru_list) {
     if (window->GetRootWindow() != viewport_->GetRootWindow())