Tab dragging as implemented as a mus API.

components/mus/public/cpp/lib/window_tree_client.cc

Index: components/mus/public/cpp/lib/window_tree_client.cc
diff --git a/components/mus/public/cpp/lib/window_tree_client.cc b/components/mus/public/cpp/lib/window_tree_client.cc
index 7a43101ff6a809ad755b710c8bb4739fd90096c1..3211d33a909540a38605a786c06bf002ebd37a9a 100644
--- a/components/mus/public/cpp/lib/window_tree_client.cc
+++ b/components/mus/public/cpp/lib/window_tree_client.cc
@@ -232,8 +232,8 @@ bool WindowTreeClient::OwnsWindow(Window* window) const {
 }
 
 void WindowTreeClient::SetBounds(Window* window,
-                                     const gfx::Rect& old_bounds,
-                                     const gfx::Rect& bounds) {
+                                 const gfx::Rect& old_bounds,
+                                 const gfx::Rect& bounds) {
   DCHECK(tree_);
   const uint32_t change_id = ScheduleInFlightChange(
       base::WrapUnique(new InFlightBoundsChange(window, old_bounds)));
@@ -580,6 +580,14 @@ void WindowTreeClient::OnReceivedCursorLocationMemory(
   DCHECK(cursor_location_mapping_);
 }
 
+void WindowTreeClient::OnWmMoveLoopCompleted(uint32_t change_id,
+                                             bool completed) {
+  if (window_manager_internal_client_) {
+    window_manager_internal_client_->OnWmMoveLoopCompleted(change_id,
+                                                           completed);
+  }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // WindowTreeClient, WindowTreeClient implementation:
 
@@ -624,6 +632,25 @@ void WindowTreeClient::SetEventObserver(mojom::EventMatcherPtr matcher) {
   }
 }
 
+void WindowTreeClient::PerformWindowMove(
+    Window* window,
+    ::mus::mojom::MoveLoopSource source,
+    const gfx::Point& cursor_location,
+    const base::Callback<void(bool)>& callback) {
+  DCHECK(on_current_move_finished_.is_null());
+  on_current_move_finished_ = callback;
+
+  current_move_loop_change_ = ScheduleInFlightChange(
+      base::WrapUnique(new InFlightMoveLoopChange(window)));
+  // Tell the window manager to take over moving us.
+  tree_->PerformWindowMove(current_move_loop_change_, window->server_id(),
+                           source, cursor_location);
+}
+
+void WindowTreeClient::CancelWindowMove(Window* window) {
+  tree_->CancelWindowMove(window->server_id());
+}
+
 Window* WindowTreeClient::NewWindow(
     const Window::SharedProperties* properties) {
   return NewWindowImpl(NewWindowType::CHILD, properties);
@@ -1019,6 +1046,12 @@ void WindowTreeClient::OnChangeCompleted(uint32_t change_id, bool success) {
   } else if (!success) {
     change->Revert();
   }
+
+  if (change_id == current_move_loop_change_) {
+    on_current_move_finished_.Run(success);
+    on_current_move_finished_.Reset();
+    current_move_loop_change_ = 0;

[sky, 2016/06/29 00:04:08]

Please move current_move_loop_change_ = 0 before the Run(), that way we don't
think we're in a move if the caller calls back.

+  }
 }
 
 void WindowTreeClient::GetWindowManager(
@@ -1069,9 +1102,9 @@ void WindowTreeClient::WmSetBounds(uint32_t change_id,
 }
 
 void WindowTreeClient::WmSetProperty(uint32_t change_id,
-                                         Id window_id,
-                                         const mojo::String& name,
-                                         mojo::Array<uint8_t> transit_data) {
+                                     Id window_id,
+                                     const mojo::String& name,
+                                     mojo::Array<uint8_t> transit_data) {
   Window* window = GetWindowByServerId(window_id);
   bool result = false;
   if (window) {
@@ -1108,7 +1141,7 @@ void WindowTreeClient::WmCreateTopLevelWindow(
 }
 
 void WindowTreeClient::WmClientJankinessChanged(ClientSpecificId client_id,
-                                                    bool janky) {
+                                                bool janky) {
   if (window_manager_delegate_) {
     auto it = embedded_windows_.find(client_id);
     CHECK(it != embedded_windows_.end());
@@ -1117,6 +1150,24 @@ void WindowTreeClient::WmClientJankinessChanged(ClientSpecificId client_id,
   }
 }
 
+void WindowTreeClient::WmPerformMoveLoop(uint32_t change_id,
+                                         Id window_id,
+                                         ::mus::mojom::MoveLoopSource source,
+                                         const gfx::Point& cursor_location) {
+  if (window_manager_delegate_) {

[sky, 2016/06/29 00:04:08]

If there is no window for id, immediately call OnWmMoveLoopCompleted.

+    window_manager_delegate_->OnWmPerformMoveLoop(
+        GetWindowByServerId(window_id), source, cursor_location,
+        base::Bind(&WindowTreeClient::OnWmMoveLoopCompleted,
+                   weak_factory_.GetWeakPtr(), change_id));
+  }
+}
+
+void WindowTreeClient::WmCancelMoveLoop(uint32_t window_id) {
+  if (window_manager_delegate_)

[sky, 2016/06/29 00:04:08]

As WmCancelMoveLoop is async, it's entirely possible that
OnWmMoveLoopCompleted() has already been called. This code should protect
against that, otherwise the delegate is going to be in a very confused state.

+    window_manager_delegate_->OnWmCancelMoveLoop(
+        GetWindowByServerId(window_id));
+}
+
 void WindowTreeClient::OnAccelerator(uint32_t id,
                                      std::unique_ptr<ui::Event> event) {
   DCHECK(event);
@@ -1132,7 +1183,7 @@ void WindowTreeClient::SetFrameDecorationValues(
 }
 
 void WindowTreeClient::SetNonClientCursor(Window* window,
-                                              mus::mojom::Cursor cursor_id) {
+                                          mus::mojom::Cursor cursor_id) {
   window_manager_internal_client_->WmSetNonClientCursor(server_id(window),
                                                         cursor_id);
 }