Reland of Reenable Tabdragging tests failing because of IsWindowPositionManaged()

ash/wm/toplevel_window_event_handler.cc

Index: ash/wm/toplevel_window_event_handler.cc
diff --git a/ash/wm/toplevel_window_event_handler.cc b/ash/wm/toplevel_window_event_handler.cc
index 5c4d9578433bf66b9d6efe8f5758529c7ee49e4c..cfc8ebffc70ae4d1cfa6270e9281e755188411f0 100644
--- a/ash/wm/toplevel_window_event_handler.cc
+++ b/ash/wm/toplevel_window_event_handler.cc
@@ -5,13 +5,16 @@
 #include "ash/wm/toplevel_window_event_handler.h"
 
 #include "ash/aura/wm_window_aura.h"
+#include "ash/common/wm/window_state.h"
 #include "ash/shell.h"
+#include "ash/wm/window_state_aura.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
+#include "ui/aura/window_tracker.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/base/cursor/cursor.h"
 #include "ui/base/hit_test.h"
@@ -87,11 +90,22 @@ aura::client::WindowMoveResult ToplevelWindowEventHandler::RunMoveLoop(
   base::MessageLoop* loop = base::MessageLoop::current();
   base::MessageLoop::ScopedNestableTaskAllower allow_nested(loop);
 
+  // Disable window position auto management while dragging and restore it
+  // aftrewards.
+  wm::WindowState* window_state = wm::GetWindowState(source);
+  const bool window_position_managed = window_state->window_position_managed();
+  window_state->set_window_position_managed(false);
+  aura::WindowTracker tracker({source});
+
   run_loop.Run();
 
   if (!weak_ptr)
     return aura::client::MOVE_CANCELED;
 
+  // Make sure the window hasn't been deleted.
+  if (tracker.Contains(source))
+    window_state->set_window_position_managed(window_position_managed);
+
   in_move_loop_ = false;
   return result == wm::WmToplevelWindowEventHandler::DragResult::SUCCESS
              ? aura::client::MOVE_SUCCESSFUL