Tab dragging as implemented as a mus API.

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

 // Copyright 2015 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 "components/mus/public/cpp/lib/in_flight_change.h"
 
 #include "components/mus/public/cpp/lib/window_private.h"
 #include "components/mus/public/cpp/window_tree_client.h"
 
 namespace mus {
@@ skipping 21 matching lines @@
 
 void InFlightBoundsChange::SetRevertValueFrom(const InFlightChange& change) {
   revert_bounds_ =
       static_cast<const InFlightBoundsChange&>(change).revert_bounds_;
 }
 
 void InFlightBoundsChange::Revert() {
   WindowPrivate(window()).LocalSetBounds(window()->bounds(), revert_bounds_);
 }
 
+// InFlightMoveLoopChange -----------------------------------------------------
+
+InFlightMoveLoopChange::InFlightMoveLoopChange(Window* window,
+                                               const gfx::Rect& revert_bounds)
+    : InFlightChange(window, ChangeType::MOVE_LOOP),
+      revert_bounds_(revert_bounds) {}
+
+void InFlightMoveLoopChange::SetRevertValueFrom(const InFlightChange& change) {
+  revert_bounds_ =
+      static_cast<const InFlightMoveLoopChange&>(change).revert_bounds_;
+}
+
+void InFlightMoveLoopChange::Revert() {
+  WindowPrivate(window()).LocalSetBounds(window()->bounds(), revert_bounds_);

[sky, 2016/06/22 23:47:56]

This is problematic because it may conflict with any InFlightBoundsChanges. For
example, consider the following scenario:
. start move loop
. Window::SetBounds (in client)
. move loop canceled

In this case you don't want to change the bounds at all.

I think you need to use an InFlightBoundsChange so revert values are properly
merged.

+}
+
 // CrashInFlightChange --------------------------------------------------------
 
 CrashInFlightChange::CrashInFlightChange(Window* window, ChangeType type)
     : InFlightChange(window, type) {}
 
 CrashInFlightChange::~CrashInFlightChange() {}
 
 void CrashInFlightChange::SetRevertValueFrom(const InFlightChange& change) {
   CHECK(false);
 }
@@ skipping 159 matching lines @@
 
 InFlightSetModalChange::~InFlightSetModalChange() {}
 
 void InFlightSetModalChange::SetRevertValueFrom(const InFlightChange& change) {}
 
 void InFlightSetModalChange::Revert() {
   WindowPrivate(window()).LocalUnsetModal();
 }
 
 }  // namespace mus