Temporarily remember the primary root window while replacing the display.

ash/display/display_manager_unittest.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 "ash/display/display_controller.h"
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
@@ skipping 374 matching lines @@
   display_manager()->OnNativeDisplaysChanged(displays);
   EXPECT_EQ(2U, display_manager()->GetNumDisplays());
 
   // and resume with different external display.
   displays.push_back(native_display);
   displays.push_back(gfx::Display(11, gfx::Rect(1, 1, 100, 100)));
   display_manager()->OnNativeDisplaysChanged(displays);
   EXPECT_EQ(2U, display_manager()->GetNumDisplays());
 }
 
+TEST_F(DisplayManagerTest, TestNativeDisplaysChangedNoInternal) {
+  EXPECT_EQ(1U, display_manager()->GetNumDisplays());
+
+  // Don't change the display info if all displays are disconnected.
+  std::vector<gfx::Display> displays;
+  display_manager()->OnNativeDisplaysChanged(displays);
+  EXPECT_EQ(1U, display_manager()->GetNumDisplays());
+
+  // Connect another display which will become primary.
+  const gfx::Display external_display(10, gfx::Rect(1, 1, 100, 100));
+  displays.push_back(external_display);
+  display_manager()->OnNativeDisplaysChanged(displays);
+  EXPECT_EQ(1U, display_manager()->GetNumDisplays());
+  EXPECT_EQ("1,1 100x100",
+            FindDisplayForId(10).bounds_in_pixel().ToString());
+}
+
 TEST_F(DisplayManagerTest, EnsurePointerInDisplays) {
   UpdateDisplay("200x200,300x300");
   Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
 
   aura::Env* env = aura::Env::GetInstance();
 
   // Set the initial position.
   root_windows[0]->MoveCursorTo(gfx::Point(350, 150));
   EXPECT_EQ("350,150", env->last_mouse_location().ToString());
 
@@ skipping 85 matching lines @@
   // OnNativeDisplaysChanged may change the display bounds.  Here makes sure
   // nothing changed if the exactly same displays are specified.
   display_manager()->OnNativeDisplaysChanged(displays);
   EXPECT_EQ("-500,0 500x500",
             FindDisplayForId(internal_display_id).bounds().ToString());
   EXPECT_EQ("0,0 100x100", FindDisplayForId(10).bounds().ToString());
 }
 
 }  // namespace internal
 }  // namespace ash