mus: Use the new drag API to implement tab dragging in chrome.

ash/mus/window_manager.cc

Index: ash/mus/window_manager.cc
diff --git a/ash/mus/window_manager.cc b/ash/mus/window_manager.cc
index 715d740ff71f043bf4bd9dcb54c15cbc44a31dcf..d0755a5720894670eba318a6c3ad8483b6ed84b9 100644
--- a/ash/mus/window_manager.cc
+++ b/ash/mus/window_manager.cc
@@ -12,6 +12,7 @@
 #include "ash/mus/bridge/wm_lookup_mus.h"
 #include "ash/mus/bridge/wm_shell_mus.h"
 #include "ash/mus/bridge/wm_window_mus.h"
+#include "ash/mus/frame/move_event_handler.h"
 #include "ash/mus/non_client_frame_controller.h"
 #include "ash/mus/property_util.h"
 #include "ash/mus/root_window_controller.h"
@@ -26,6 +27,7 @@
 #include "services/ui/public/cpp/window_tree_client.h"
 #include "services/ui/public/interfaces/mus_constants.mojom.h"
 #include "services/ui/public/interfaces/window_manager.mojom.h"
+#include "ui/base/hit_test.h"
 #include "ui/events/mojo/event.mojom.h"
 #include "ui/views/mus/screen_mus.h"
 
@@ -235,11 +237,26 @@ void WindowManager::OnWmPerformMoveLoop(
     ::ui::mojom::MoveLoopSource source,
     const gfx::Point& cursor_location,
     const base::Callback<void(bool)>& on_done) {
-  NOTIMPLEMENTED();
+  WmWindowMus* child_window = WmWindowMus::Get(window);
+  MoveEventHandler* handler = MoveEventHandler::GetForWindow(child_window);
+  if (!handler) {
+    on_done.Run(false);
+    return;
+  }
+
+  DCHECK(!handler->IsDragInProgress());
+  aura::client::WindowMoveSource aura_source =
+      source == ::ui::mojom::MoveLoopSource::MOUSE
+          ? aura::client::WINDOW_MOVE_SOURCE_MOUSE
+          : aura::client::WINDOW_MOVE_SOURCE_TOUCH;
+  handler->AttemptToStartDrag(cursor_location, HTCAPTION, aura_source, on_done);
 }
 
 void WindowManager::OnWmCancelMoveLoop(::ui::Window* window) {
-  NOTIMPLEMENTED();
+  WmWindowMus* child_window = WmWindowMus::Get(window);
+  MoveEventHandler* handler = MoveEventHandler::GetForWindow(child_window);
+  if (handler)
+    handler->RevertDrag();
 }
 
 ui::mojom::EventResult WindowManager::OnAccelerator(uint32_t id,
@@ -253,6 +270,7 @@ ui::mojom::EventResult WindowManager::OnAccelerator(uint32_t id,
                         OnAccelerator(id, event));
       break;
   }
+
   return ui::mojom::EventResult::HANDLED;
 }