Clear the software mirroring display list when adding it to the updated list.

ash/display/display_manager.cc

 // Copyright (c) 2012 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 "ash/display/display_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <set>
 #include <string>
@@ skipping 1203 matching lines @@
     return &(*iter);
   // TODO(oshima): This happens when a windows in unified desktop have
   // been moved to normal window. Fix this.
   if (id != kUnifiedDisplayId)
     DLOG(WARNING) << "Could not find display:" << id;
   return nullptr;
 }
 
 void DisplayManager::AddMirrorDisplayInfoIfAny(
     std::vector<DisplayInfo>* display_info_list) {
-  if (software_mirroring_enabled() && IsInMirrorMode())
+  if (software_mirroring_enabled() && IsInMirrorMode()) {
     display_info_list->push_back(GetDisplayInfo(mirroring_display_id_));
+    software_mirroring_display_list_.clear();
+  }
 }
 
 void DisplayManager::InsertAndUpdateDisplayInfo(const DisplayInfo& new_info) {
   std::map<int64_t, DisplayInfo>::iterator info =
       display_info_.find(new_info.id());
   if (info != display_info_.end()) {
     info->second.Copy(new_info);
   } else {
     display_info_[new_info.id()] = new_info;
     display_info_[new_info.id()].set_native(false);
@@ skipping 159 matching lines @@
 
   return old_bounds != target_display->bounds();
 }
 
 void DisplayManager::RunPendingTasksForTest() {
   if (!software_mirroring_display_list_.empty())
     base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace ash