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 3a7e71dbcb9a8cf5fb213b702df2627165e113b6..9a5ff2685fd5a4a2f52ce37e8e5be5497c5e1245 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)));
@@ -624,6 +624,26 @@ void WindowTreeClient::SetEventObserver(mojom::EventMatcherPtr matcher) {
   }
 }
 
+void WindowTreeClient::PerformWindowMove(
+    Window* window,
+    const gfx::Point& cursor_location,
+    const base::Callback<void(bool)>& callback) {
+  if (!on_current_move_finished_.is_null()) {
+    NOTREACHED();
+    callback.Run(false);

[sky, 2016/06/24 19:59:00]

Why are you calling callback.Run(false) here? I recommend either making 631 a
DCHECK, or if you really want to handle starting another move loop then we you
need a cancel api.

+  }
+  on_current_move_finished_ = callback;
+
+  const uint32_t change_id = ScheduleInFlightChange(
+      base::WrapUnique(new InFlightMoveLoopChange(window)));
+  // Tell the window manager to take over moving us.
+  tree_->PerformWindowMove(change_id, window->server_id(), cursor_location);
+}
+
+void WindowTreeClient::CancelWindowMove(Window* window) {
+  tree_->CancelWindowMove(window->server_id());
+}
+
 Window* WindowTreeClient::NewWindow(
     const Window::SharedProperties* properties) {
   return NewWindowImpl(NewWindowType::CHILD, properties);
@@ -1021,6 +1041,16 @@ void WindowTreeClient::OnChangeCompleted(uint32_t change_id, bool success) {
   }
 }
 
+void WindowTreeClient::OnMoveLoopCompleted(uint32_t change_id, bool success) {
+  std::unique_ptr<InFlightChange> change(std::move(in_flight_map_[change_id]));
+  in_flight_map_.erase(change_id);
+  if (!change)
+    return;
+
+  on_current_move_finished_.Run(success);
+  on_current_move_finished_.Reset();
+}
+
 void WindowTreeClient::GetWindowManager(
     mojo::AssociatedInterfaceRequest<WindowManager> internal) {
   window_manager_internal_.reset(
@@ -1069,9 +1099,9 @@ 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 +1138,7 @@ 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 +1147,19 @@ void WindowTreeClient::WmClientJankinessChanged(ClientSpecificId client_id,
   }
 }
 
+void WindowTreeClient::WmPerformMoveLoop(uint32_t change_id,
+                                         Id window_id,
+                                         const gfx::Point& cursor_location) {
+  if (window_manager_delegate_)
+    window_manager_delegate_->OnWmPerformMoveLoop(change_id, window_id,

[sky, 2016/06/24 19:59:00]

This and OnWmCancelMoveLoop() should take the window, not a window_id. Also, the
delegate shouldn't need the change_id, it should be cached here and then
implicitly used in OnWmMoveLoopCompleted (or if you prefer supply a callback to
OnWmPerformMoveLoop that binds the change_id.

+                                                  cursor_location);
+}
+
+void WindowTreeClient::WmCancelMoveLoop(uint32_t window_id) {
+  if (window_manager_delegate_)
+    window_manager_delegate_->OnWmCancelMoveLoop(window_id);
+}
+
 void WindowTreeClient::OnAccelerator(uint32_t id,
                                      std::unique_ptr<ui::Event> event) {
   DCHECK(event);
@@ -1132,7 +1175,7 @@ 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);
 }
@@ -1178,4 +1221,12 @@ void WindowTreeClient::SetUnderlaySurfaceOffsetAndExtendedHitArea(
   }
 }
 
+void WindowTreeClient::OnWmMoveLoopCompleted(uint32_t change_id,
+                                             bool completed) {
+  if (window_manager_internal_client_) {
+    window_manager_internal_client_->OnWmMoveLoopCompleted(change_id,
+                                                           completed);
+  }
+}
+
 }  // namespace mus