[mus+ash] Removes WmWindow from ash/wm/focus_rules

With this CL WmWindow is no longer used in ash/wm.

BUG=722553
TEST=None (refactoring)

Review-Url: https://codereview.chromium.org/2908643003
Cr-Commit-Position: refs/heads/master@{#475121}
diff --git a/ash/shell/shell_delegate_impl.h b/ash/shell/shell_delegate_impl.h
index dbc15971..f768cea 100644
--- a/ash/shell/shell_delegate_impl.h
+++ b/ash/shell/shell_delegate_impl.h
@@ -28,7 +28,7 @@
   bool IsIncognitoAllowed() const override;
   bool IsMultiProfilesEnabled() const override;
   bool IsRunningInForcedAppMode() const override;
-  bool CanShowWindowForUser(WmWindow* window) const override;
+  bool CanShowWindowForUser(aura::Window* window) const override;
   bool IsForceMaximizeOnFirstRun() const override;
   void PreInit() override;
   void PreShutdown() override;