mus: Let clients set the cursor of their window.

components/mus/public/cpp/window.h

Index: components/mus/public/cpp/window.h
diff --git a/components/mus/public/cpp/window.h b/components/mus/public/cpp/window.h
index 9da43ce6f31e9c5d07e5cb7dde6f8d78401be0c0..668b703cbff468fe49546a91b7333101bb1e1c7b 100644
--- a/components/mus/public/cpp/window.h
+++ b/components/mus/public/cpp/window.h
@@ -78,6 +78,10 @@ class Window {
   bool visible() const { return visible_; }
   void SetVisible(bool value);
 
+  // Cursors
+  mojom::Cursor predefined_cursor() const { return cursor_id_; }
+  void SetPredefinedCursor(mus::mojom::Cursor cursor_id);
+
   // A Window is drawn if the Window and all its ancestors are visible and the
   // Window is attached to the root.
   bool IsDrawn() const;
@@ -224,6 +228,7 @@ class Window {
                                const mojom::ViewportMetrics& new_metrics);
   void LocalSetDrawn(bool drawn);
   void LocalSetVisible(bool visible);
+  void LocalSetPredefinedCursor(mojom::Cursor cursor_id);
   void LocalSetSharedProperty(const std::string& name,
                               const std::vector<uint8_t>* data);
 
@@ -276,6 +281,8 @@ class Window {
 
   bool visible_;
 
+  mojom::Cursor cursor_id_;
+
   SharedProperties properties_;
 
   // Drawn state is derived from the visible state and the parent's visible