mus: Implement interwindow drag and drop

services/ui/public/cpp/window.cc

Index: services/ui/public/cpp/window.cc
diff --git a/services/ui/public/cpp/window.cc b/services/ui/public/cpp/window.cc
index f7d32f72abfa1adbb791d7e89b9c5591869160de..731a773e410d13815e0355275eb52b695ff7c156 100644
--- a/services/ui/public/cpp/window.cc
+++ b/services/ui/public/cpp/window.cc
@@ -447,6 +447,14 @@ void Window::SetCanFocus(bool can_focus) {
     client_->SetCanFocus(server_id_, can_focus);
 }
 
+void Window::SetCanAcceptDrops(WindowDropTarget* drop_target) {
+  if (drop_target_ == drop_target)
+    return;
+  drop_target_ = drop_target;
+  if (client_)
+    client_->SetCanAcceptDrops(server_id_, !!drop_target_);
+}
+
 void Window::SetCanAcceptEvents(bool can_accept_events) {
   if (can_accept_events_ == can_accept_events)
     return;
@@ -473,6 +481,17 @@ void Window::RequestClose() {
     client_->RequestClose(this);
 }
 
+void Window::PerformDragDrop(
+    int drag_pointer,
+    const std::map<std::string, std::vector<uint8_t>>& drag_data,
+    int drag_operation,
+    const gfx::Point& cursor_location,
+    const SkBitmap& bitmap,
+    const base::Callback<void(bool)>& callback) {
+  client_->PerformDragDrop(this, drag_pointer, drag_data, drag_operation,
+                           cursor_location, bitmap, callback);
+}
+
 void Window::PerformWindowMove(mojom::MoveLoopSource source,
                                const gfx::Point& cursor_location,
                                const base::Callback<void(bool)>& callback) {