Tab dragging as implemented as a mus API.

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 3cf965e2565a3ff23de60cee5ab9f54ad72c4dd0..71cde8c1b21f8ac2cdbd0fb55010c7a3208a30bc 100644
--- a/components/mus/public/cpp/window.h
+++ b/components/mus/public/cpp/window.h
@@ -221,6 +221,16 @@ class Window {
   // to a better place.
   void RequestClose();
 
+  // Tells the window manager to take control of moving the window. Locally,
+  // this spins up a nested message loop to handle all further ui messages; we
+  // don't use mojo's built in sync messages because we explicitly want to
+  // process all other messages. Returns true if the move wasn't canceled.
+  bool PerformWindowMove(const gfx::Point& cursor_location);
+
+  // Tells the window manager to abort any current move initiated by
+  // PerformWindowMove().
+  void CancelWindowMove();
+
   // Returns an internal name, set by a client app when it creates a window.
   std::string GetName() const;