Revert "Add AppWindow.setVisibleOnAllWorkspaces." (https://codereview.chromium.org/469993003)

extensions/browser/app_window/native_app_window.h

Index: extensions/browser/app_window/native_app_window.h
diff --git a/extensions/browser/app_window/native_app_window.h b/extensions/browser/app_window/native_app_window.h
index b5007dde4f80b26c4be88fe484f5c7b6e98d4853..afd65c5cc8f863a94c1cce2f422b2c853665e81e 100644
--- a/extensions/browser/app_window/native_app_window.h
+++ b/extensions/browser/app_window/native_app_window.h
@@ -92,9 +92,6 @@ class NativeAppWindow : public ui::BaseWindow,
   virtual void SetContentSizeConstraints(const gfx::Size& min_size,
                                          const gfx::Size& max_size) = 0;
 
-  // Returns whether the window show be visible on all workspaces.
-  virtual void SetVisibleOnAllWorkspaces(bool always_visible) = 0;
-
   // Returns false if the underlying native window ignores alpha transparency
   // when compositing.
   virtual bool CanHaveAlphaEnabled() const = 0;