mash: Use the new mus drag and drop API to get drag working in mash.

services/ui/ws/window_manager_state.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "services/ui/ws/window_manager_state.h"
 
 #include <utility>
 
 #include "base/memory/weak_ptr.h"
 #include "services/shell/public/interfaces/connector.mojom.h"
@@ skipping 144 matching lines @@
 }
 
 void WindowManagerState::ReleaseCaptureBlockedByAnyModalWindow() {
   event_dispatcher_.ReleaseCaptureBlockedByAnyModalWindow();
 }
 
 void WindowManagerState::SetDragDropSourceWindow(
     DragSource* drag_source,
     ServerWindow* window,
     DragTargetConnection* source_connection,
-    int32_t drag_pointer,
     mojo::Map<mojo::String, mojo::Array<uint8_t>> drag_data,
     uint32_t drag_operation) {
+  int32_t drag_pointer = PointerEvent::kMousePointerId;
+  if (event_awaiting_input_ack_ &&
+      event_awaiting_input_ack_->IsPointerEvent()) {
+    drag_pointer = event_awaiting_input_ack_->AsPointerEvent()->pointer_id();
+  } else {
+    NOTIMPLEMENTED() << "Set drag drop set up during something other than a "
+                     << "pointer event; rejecting drag.";
+    drag_source->OnDragCompleted(false, ui::mojom::kDropEffectNone);
+    return;
+  }
+
   event_dispatcher_.SetDragDropSourceWindow(
       drag_source, window, source_connection, drag_pointer,
       std::move(drag_data), drag_operation);
 }
 
 void WindowManagerState::CancelDragDrop() {
   event_dispatcher_.CancelDragDrop();
 }
 
 void WindowManagerState::EndDragDrop() {
@@ skipping 230 matching lines @@
       display_root->display()->UpdateNativeCursor(cursor_id);
     }
   }
 
   event_dispatch_phase_ = EventDispatchPhase::TARGET;
 
   WindowTree* tree = window_server()->GetTreeWithId(client_id);
   DCHECK(tree);
   ScheduleInputEventTimeout(tree);
 
-  if (accelerator) {
-    event_awaiting_input_ack_ = ui::Event::Clone(event);
+  event_awaiting_input_ack_ = ui::Event::Clone(event);
+
+  if (accelerator)
     post_target_accelerator_ = accelerator;
-  }
 
   // Ignore |tree| because it will receive the event via normal dispatch.
   window_server()->SendToPointerWatchers(event, user_id(), target, tree);
 
   tree->DispatchInputEvent(target, event);
 }
 
 void WindowManagerState::AddDebugAccelerators() {
   const DebugAccelerator accelerator = {
       DebugAcceleratorType::PRINT_WINDOWS, ui::VKEY_S,
@@ skipping 187 matching lines @@
       window->RemoveObserver(this);
       orphaned_window_manager_display_roots_.erase(iter);
       return;
     }
   }
   NOTREACHED();
 }
 
 }  // namespace ws
 }  // namespace ui