Close mirroring window only when necessary

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 655 matching lines @@
       ": Multiple display test does not work on Windows bots. Please "
       "skip (don't disable) the test using SupportsMultipleDisplays()";
 #endif
 
   DisplayInfoList new_display_info_list = updated_display_info_list;
   std::sort(active_display_list_.begin(), active_display_list_.end(),
             DisplaySortFunctor());
   std::sort(new_display_info_list.begin(),
             new_display_info_list.end(),
             DisplayInfoSortFunctor());
+
+  CreateSoftwareMirroringDisplayInfo(&new_display_info_list);
+
   // Close the mirroring window if any here to avoid creating two compositor on
   // one display.
   if (delegate_)
-    delegate_->CloseMirroringDisplay();
-
-  CreateSoftwareMirroringDisplay(&new_display_info_list);
+    delegate_->CloseMirroringDisplayIfNotNecessary();
 
   DisplayList new_displays;
   DisplayList removed_displays;
   std::map<size_t, uint32_t> display_changes;
   std::vector<size_t> added_display_indices;
 
   DisplayList::iterator curr_iter = active_display_list_.begin();
   DisplayInfoList::const_iterator new_info_iter = new_display_info_list.begin();
 
   while (curr_iter != active_display_list_.end() ||
@@ skipping 384 matching lines @@
   }
 }
 
 void DisplayManager::UpdateInternalDisplayModeListForTest() {
   if (display_info_.count(gfx::Display::InternalDisplayId()) == 0)
     return;
   DisplayInfo* info = &display_info_[gfx::Display::InternalDisplayId()];
   SetInternalDisplayModeList(info);
 }
 
-void DisplayManager::CreateSoftwareMirroringDisplay(
+void DisplayManager::CreateSoftwareMirroringDisplayInfo(
     DisplayInfoList* display_info_list) {
   // Use the internal display or 1st as the mirror source, then scale
   // the root window so that it matches the external display's
   // resolution. This is necessary in order for scaling to work while
   // mirrored.
   if (display_info_list->size() == 2) {
     switch (multi_display_mode_) {
       case MIRRORING: {
         bool zero_is_source =
             first_display_id_ == (*display_info_list)[0].id() ||
@@ skipping 217 matching lines @@
       gfx::Rect(new_secondary_origin, secondary_bounds.size()));
   secondary_display->UpdateWorkAreaFromInsets(insets);
 }
 
 void DisplayManager::RunPendingTasksForTest() {
   if (!software_mirroring_display_list_.empty())
     base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace ash