Update mirroring display even if the display configurations that are visible to ash/chrome hasn't c…

ash/display/display_manager_unittest.cc

Index: ash/display/display_manager_unittest.cc
diff --git a/ash/display/display_manager_unittest.cc b/ash/display/display_manager_unittest.cc
index ae5c192764b2419ec4d5fba84efac8a88988b5dd..3d3bbec4caf873e10deea0e02ce10bdb3162b233 100644
--- a/ash/display/display_manager_unittest.cc
+++ b/ash/display/display_manager_unittest.cc
@@ -9,6 +9,7 @@
 #include "ash/display/display_info.h"
 #include "ash/display/display_layout_store.h"
 #include "ash/display/display_util.h"
+#include "ash/display/mirror_window_controller.h"
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
@@ -1342,6 +1343,27 @@ TEST_F(DisplayManagerTest, SoftwareMirroring) {
   Shell::GetScreen()->RemoveObserver(&display_observer);
 }
 
+TEST_F(DisplayManagerTest, SingleDisplayToSoftwareMirroring) {
+  if (!SupportsMultipleDisplays())
+    return;
+  UpdateDisplay("600x400");
+
+  DisplayManager* display_manager = Shell::GetInstance()->display_manager();
+  display_manager->SetSecondDisplayMode(DisplayManager::MIRRORING);
+  UpdateDisplay("600x400,600x400");
+
+  EXPECT_TRUE(display_manager->IsMirrored());
+  EXPECT_EQ(1U, display_manager->GetNumDisplays());
+  DisplayController* display_controller =
+      ash::Shell::GetInstance()->display_controller();
+  EXPECT_TRUE(display_controller->mirror_window_controller()->GetWindow());
+
+  UpdateDisplay("600x400");
+  EXPECT_FALSE(display_manager->IsMirrored());
+  EXPECT_EQ(1U, display_manager->GetNumDisplays());
+  EXPECT_FALSE(display_controller->mirror_window_controller()->GetWindow());
+}
+
 #if defined(OS_CHROMEOS)
 // Make sure this does not cause any crashes. See http://crbug.com/412910
 // This test is limited to OS_CHROMEOS because CursorCompositingEnabled is only