Allow dynamic enabling/disabling of unified desktop

The default multi display is stored in the layout store first, and which is used by UpdateDisplays later.
Hence no need to update this layout information in
WindowTreeHostManager. current_default_multi_display_mode_ is still necessary because it's also used when switching to/from mirror mode.

This also fixed a bug in the logic to short ids.

BUG=515607
TEST=covered by unittests. manual

Review URL: https://codereview.chromium.org/1261693004

Cr-Commit-Position: refs/heads/master@{#341452}

28 files changed, 204 insertions, 148 deletions

diff --git a/ash/accelerators/accelerator_controller.cc b/ash/accelerators/accelerator_controller.cc
index 6ef3ac6..5141766 100644
--- a/ash/accelerators/accelerator_controller.cc
+++ b/ash/accelerators/accelerator_controller.cc
@@ -851,6 +851,7 @@ bool AcceleratorController::CanPerformAction(
       return CanHandlePositionCenter();
 #if defined(OS_CHROMEOS)
     case DEBUG_ADD_REMOVE_DISPLAY:
+    case DEBUG_TOGGLE_UNIFIED_DESKTOP:
       return debug::DebugAcceleratorsEnabled();
     case DISABLE_CAPS_LOCK:
       return CanHandleDisableCapsLock(previous_accelerator);
@@ -1107,6 +1108,9 @@ void AcceleratorController::PerformAction(AcceleratorAction action,
     case DEBUG_ADD_REMOVE_DISPLAY:
       debug::PerformDebugActionIfEnabled(action);
       break;
+    case DEBUG_TOGGLE_UNIFIED_DESKTOP:
+      debug::PerformDebugActionIfEnabled(action);
+      break;
     case DISABLE_CAPS_LOCK:
       HandleDisableCapsLock();
       break;
diff --git a/ash/accelerators/accelerator_table.cc b/ash/accelerators/accelerator_table.cc
index f3a0a49..3f02fcc 100644
--- a/ash/accelerators/accelerator_table.cc
+++ b/ash/accelerators/accelerator_table.cc
@@ -179,50 +179,58 @@ const size_t kAcceleratorDataLength = arraysize(kAcceleratorData);
 
 const AcceleratorData kDebugAcceleratorData[] = {
 #if defined(OS_CHROMEOS)
-  // Extra shortcut for debug build to control magnifier on linux desktop.
-  { true, ui::VKEY_BRIGHTNESS_DOWN, ui::EF_CONTROL_DOWN,
-    MAGNIFY_SCREEN_ZOOM_OUT},
-  { true, ui::VKEY_BRIGHTNESS_UP, ui::EF_CONTROL_DOWN, MAGNIFY_SCREEN_ZOOM_IN},
-  // Extra shortcuts to lock the screen on linux desktop.
-  { true, ui::VKEY_L, ui::EF_ALT_DOWN, LOCK_SCREEN },
-  { true, ui::VKEY_POWER, ui::EF_SHIFT_DOWN, LOCK_PRESSED },
-  { false, ui::VKEY_POWER, ui::EF_SHIFT_DOWN, LOCK_RELEASED },
-  { true, ui::VKEY_D, ui::EF_CONTROL_DOWN | ui::EF_SHIFT_DOWN,
-    DEBUG_ADD_REMOVE_DISPLAY },
-  { true, ui::VKEY_M, ui::EF_CONTROL_DOWN | ui::EF_SHIFT_DOWN,
-    TOGGLE_MIRROR_MODE },
-  { true, ui::VKEY_W, ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN, TOGGLE_WIFI },
-  // Extra shortcut for display swapping as alt-f4 is taken on linux desktop.
-  { true, ui::VKEY_S, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN,
-    SWAP_PRIMARY_DISPLAY },
+    // Extra shortcut for debug build to control magnifier on linux desktop.
+    {true, ui::VKEY_BRIGHTNESS_DOWN, ui::EF_CONTROL_DOWN,
+     MAGNIFY_SCREEN_ZOOM_OUT},
+    {true, ui::VKEY_BRIGHTNESS_UP, ui::EF_CONTROL_DOWN, MAGNIFY_SCREEN_ZOOM_IN},
+    // Extra shortcuts to lock the screen on linux desktop.
+    {true, ui::VKEY_L, ui::EF_ALT_DOWN, LOCK_SCREEN},
+    {true, ui::VKEY_POWER, ui::EF_SHIFT_DOWN, LOCK_PRESSED},
+    {false, ui::VKEY_POWER, ui::EF_SHIFT_DOWN, LOCK_RELEASED},
+    {true, ui::VKEY_D, ui::EF_CONTROL_DOWN | ui::EF_SHIFT_DOWN,
+     DEBUG_ADD_REMOVE_DISPLAY},
+    {true, ui::VKEY_J, ui::EF_CONTROL_DOWN | ui::EF_SHIFT_DOWN,
+     DEBUG_TOGGLE_UNIFIED_DESKTOP},
+    {true, ui::VKEY_M, ui::EF_CONTROL_DOWN | ui::EF_SHIFT_DOWN,
+     TOGGLE_MIRROR_MODE},
+    {true, ui::VKEY_W, ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN, TOGGLE_WIFI},
+    // Extra shortcut for display swapping as alt-f4 is taken on linux desktop.
+    {true, ui::VKEY_S, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN,
+     SWAP_PRIMARY_DISPLAY},
 #endif
-  // Extra shortcut to rotate/scale up/down the screen on linux desktop.
-  { true, ui::VKEY_R,
-    ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN, ROTATE_SCREEN },
-  // For testing on systems where Alt-Tab is already mapped.
-  { true, ui::VKEY_W, ui::EF_ALT_DOWN, CYCLE_FORWARD_MRU },
-  { true, ui::VKEY_F11, ui::EF_CONTROL_DOWN,
-    DEBUG_TOGGLE_ROOT_WINDOW_FULL_SCREEN },
-  { true, ui::VKEY_W, ui::EF_SHIFT_DOWN | ui::EF_ALT_DOWN,
-      CYCLE_BACKWARD_MRU },
-  { true, ui::VKEY_B, ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_TOGGLE_DESKTOP_BACKGROUND_MODE },
-  { true, ui::VKEY_F, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN,
-    TOGGLE_FULLSCREEN },
-  { true, ui::VKEY_L, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_PRINT_LAYER_HIERARCHY },
-  { true, ui::VKEY_V, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_PRINT_VIEW_HIERARCHY },
-  { true, ui::VKEY_W, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_PRINT_WINDOW_HIERARCHY },
-  { true, ui::VKEY_S, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_TOGGLE_DEVICE_SCALE_FACTOR },
-  { true, ui::VKEY_B, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_TOGGLE_SHOW_DEBUG_BORDERS },
-  { true, ui::VKEY_F, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_TOGGLE_SHOW_FPS_COUNTER },
-  { true, ui::VKEY_P, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
-    DEBUG_TOGGLE_SHOW_PAINT_RECTS },
+    // Extra shortcut to rotate/scale up/down the screen on linux desktop.
+    {true, ui::VKEY_R,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN, ROTATE_SCREEN},
+    // For testing on systems where Alt-Tab is already mapped.
+    {true, ui::VKEY_W, ui::EF_ALT_DOWN, CYCLE_FORWARD_MRU},
+    {true, ui::VKEY_F11, ui::EF_CONTROL_DOWN,
+     DEBUG_TOGGLE_ROOT_WINDOW_FULL_SCREEN},
+    {true, ui::VKEY_W, ui::EF_SHIFT_DOWN | ui::EF_ALT_DOWN, CYCLE_BACKWARD_MRU},
+    {true, ui::VKEY_B, ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_TOGGLE_DESKTOP_BACKGROUND_MODE},
+    {true, ui::VKEY_F, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN,
+     TOGGLE_FULLSCREEN},
+    {true, ui::VKEY_L,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_PRINT_LAYER_HIERARCHY},
+    {true, ui::VKEY_V,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_PRINT_VIEW_HIERARCHY},
+    {true, ui::VKEY_W,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_PRINT_WINDOW_HIERARCHY},
+    {true, ui::VKEY_S,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_TOGGLE_DEVICE_SCALE_FACTOR},
+    {true, ui::VKEY_B,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_TOGGLE_SHOW_DEBUG_BORDERS},
+    {true, ui::VKEY_F,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_TOGGLE_SHOW_FPS_COUNTER},
+    {true, ui::VKEY_P,
+     ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN | ui::EF_ALT_DOWN,
+     DEBUG_TOGGLE_SHOW_PAINT_RECTS},
 };
 
 const size_t kDebugAcceleratorDataLength = arraysize(kDebugAcceleratorData);
diff --git a/ash/accelerators/accelerator_table.h b/ash/accelerators/accelerator_table.h
index 86ec318..089e240 100644
--- a/ash/accelerators/accelerator_table.h
+++ b/ash/accelerators/accelerator_table.h
@@ -112,6 +112,7 @@ enum AcceleratorAction {
   BRIGHTNESS_DOWN,
   BRIGHTNESS_UP,
   DEBUG_ADD_REMOVE_DISPLAY,
+  DEBUG_TOGGLE_UNIFIED_DESKTOP,
   DISABLE_CAPS_LOCK,
   DISABLE_GPU_WATCHDOG,
   KEYBOARD_BRIGHTNESS_DOWN,
diff --git a/ash/accelerators/debug_commands.cc b/ash/accelerators/debug_commands.cc
index 5ce0c7c..fe4589d 100644
--- a/ash/accelerators/debug_commands.cc
+++ b/ash/accelerators/debug_commands.cc
@@ -148,6 +148,10 @@ void PerformDebugActionIfEnabled(AcceleratorAction action) {
     case DEBUG_ADD_REMOVE_DISPLAY:
       Shell::GetInstance()->display_manager()->AddRemoveDisplay();
       break;
+    case DEBUG_TOGGLE_UNIFIED_DESKTOP:
+      Shell::GetInstance()->display_manager()->SetUnifiedDesktopEnabled(
+          !Shell::GetInstance()->display_manager()->unified_desktop_enabled());
+      break;
 #endif
     case DEBUG_PRINT_LAYER_HIERARCHY:
       HandlePrintLayerHierarchy();
diff --git a/ash/ash_switches.cc b/ash/ash_switches.cc
index 14e79cb..fdbe279 100644
--- a/ash/ash_switches.cc
+++ b/ash/ash_switches.cc
@@ -136,11 +136,6 @@ bool ConstrainPointerToRoot() {
              kAshConstrainPointerToRoot);
 }
 
-bool UnifiedDesktopEnabled() {
-  return base::CommandLine::ForCurrentProcess()->HasSwitch(
-      kAshEnableUnifiedDesktop);
-}
-
 #endif
 
 }  // namespace switches
diff --git a/ash/ash_switches.h b/ash/ash_switches.h
index 0b5e030..ed8f878 100644
--- a/ash/ash_switches.h
+++ b/ash/ash_switches.h
@@ -51,8 +51,6 @@ ASH_EXPORT extern const char kForceAshToDesktop[];
 #if defined(OS_CHROMEOS)
 // True if the pointer (cursor) position should be kept inside root windows.
 ASH_EXPORT bool ConstrainPointerToRoot();
-
-ASH_EXPORT bool UnifiedDesktopEnabled();
 #endif
 
 }  // namespace switches
diff --git a/ash/display/display_layout.cc b/ash/display/display_layout.cc
index 2cf54a6..9816f21 100644
--- a/ash/display/display_layout.cc
+++ b/ash/display/display_layout.cc
@@ -5,7 +5,9 @@
 #include "ash/display/display_layout.h"
 
 #include "ash/ash_switches.h"
+#include "ash/display/display_manager.h"
 #include "ash/display/display_pref_util.h"
+#include "ash/shell.h"
 #include "base/json/json_value_converter.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
@@ -72,7 +74,7 @@ DisplayLayout::DisplayLayout()
       offset(0),
       mirrored(false),
 #if defined(OS_CHROMEOS)
-      default_unified(switches::UnifiedDesktopEnabled()),
+      default_unified(true),
 #else
       default_unified(false),
 #endif
@@ -84,7 +86,7 @@ DisplayLayout::DisplayLayout(DisplayLayout::Position position, int offset)
       offset(offset),
       mirrored(false),
 #if defined(OS_CHROMEOS)
-      default_unified(switches::UnifiedDesktopEnabled()),
+      default_unified(true),
 #else
       default_unified(false),
 #endif
@@ -146,9 +148,13 @@ bool DisplayLayout::ConvertToValue(const DisplayLayout& layout,
 
 std::string DisplayLayout::ToString() const {
   const std::string position_str = GetStringFromPosition(position);
+  bool unified =
+      default_unified &&
+      Shell::GetInstance()->display_manager()->unified_desktop_enabled();
+
   return base::StringPrintf("%s, %d%s%s", position_str.c_str(), offset,
                             mirrored ? ", mirrored" : "",
-                            default_unified ? ", unified" : "");
+                            unified ? ", unified" : "");
 }
 
 // static
diff --git a/ash/display/display_layout.h b/ash/display/display_layout.h
index df966b2..e5623f4 100644
--- a/ash/display/display_layout.h
+++ b/ash/display/display_layout.h
@@ -66,6 +66,7 @@ struct ASH_EXPORT DisplayLayout {
   int64 primary_id;
 
   // Returns string representation of the layout for debugging/testing.
+  // This includes "unified" only if the unified desktop feature is enabled.
   std::string ToString() const;
 };
 
diff --git a/ash/display/display_layout_store.cc b/ash/display/display_layout_store.cc
index 2f5dc2b..c002e04 100644
--- a/ash/display/display_layout_store.cc
+++ b/ash/display/display_layout_store.cc
@@ -51,11 +51,6 @@ void DisplayLayoutStore::RegisterLayoutForDisplayIdPair(
     const DisplayLayout& layout) {
   auto key = CreateDisplayIdPair(id1, id2);
   paired_layouts_[key] = layout;
-#if defined(OS_CHROMEOS)
-  // Force disabling unified desktop if the flag is not set.
-  if (!switches::UnifiedDesktopEnabled())
-    paired_layouts_[key].default_unified = false;
-#endif
 }
 
 DisplayLayout DisplayLayoutStore::GetRegisteredDisplayLayout(
diff --git a/ash/display/display_manager.cc b/ash/display/display_manager.cc
index 88987f0..dba2e0a 100644
--- a/ash/display/display_manager.cc
+++ b/ash/display/display_manager.cc
@@ -51,8 +51,6 @@
 #include "base/win/windows_version.h"
 #endif
 
-#include "base/debug/stack_trace.h"
-
 namespace ash {
 typedef std::vector<gfx::Display> DisplayList;
 typedef std::vector<DisplayInfo> DisplayInfoList;
@@ -69,13 +67,13 @@ const int kMinimumOverlapForInvalidOffset = 100;
 
 struct DisplaySortFunctor {
   bool operator()(const gfx::Display& a, const gfx::Display& b) {
-    return a.id() < b.id();
+    return CompareDisplayIds(a.id(), b.id());
   }
 };
 
 struct DisplayInfoSortFunctor {
   bool operator()(const DisplayInfo& a, const DisplayInfo& b) {
-    return a.id() < b.id();
+    return CompareDisplayIds(a.id(), b.id());
   }
 };
 
@@ -137,13 +135,16 @@ DisplayManager::DisplayManager()
       force_bounds_changed_(false),
       change_display_upon_host_resize_(false),
       multi_display_mode_(EXTENDED),
-      default_multi_display_mode_(EXTENDED),
+      current_default_multi_display_mode_(EXTENDED),
       mirroring_display_id_(gfx::Display::kInvalidDisplayID),
       registered_internal_display_rotation_lock_(false),
       registered_internal_display_rotation_(gfx::Display::ROTATE_0),
+      unified_desktop_enabled_(false),
       weak_ptr_factory_(this) {
 #if defined(OS_CHROMEOS)
   change_display_upon_host_resize_ = !base::SysInfo::IsRunningOnChromeOS();
+  unified_desktop_enabled_ = base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kAshEnableUnifiedDesktop);
 #endif
   gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_ALTERNATE, screen_.get());
   gfx::Screen* current_native =
@@ -621,19 +622,14 @@ void DisplayManager::OnNativeDisplaysChanged(
   }
 
 #if defined(OS_CHROMEOS)
-  if (new_display_info_list.size() > 1) {
-    std::sort(new_display_info_list.begin(), new_display_info_list.end(),
-              DisplayInfoSortFunctor());
+  if (!base::SysInfo::IsRunningOnChromeOS() &&
+      new_display_info_list.size() > 1) {
     DisplayIdPair pair = CreateDisplayIdPair(new_display_info_list[0].id(),
                                              new_display_info_list[1].id());
     DisplayLayout layout = layout_store_->GetRegisteredDisplayLayout(pair);
-    default_multi_display_mode_ =
-        (layout.default_unified && switches::UnifiedDesktopEnabled())
-            ? UNIFIED
-            : EXTENDED;
     // Mirror mode is set by DisplayConfigurator on the device.
     // Emulate it when running on linux desktop.
-    if (!base::SysInfo::IsRunningOnChromeOS() && layout.mirrored)
+    if (layout.mirrored)
       SetMultiDisplayMode(MIRRORING);
   }
 #endif
@@ -664,8 +660,17 @@ void DisplayManager::UpdateDisplays(
             new_display_info_list.end(),
             DisplayInfoSortFunctor());
 
+  if (new_display_info_list.size() > 1) {
+    DisplayIdPair pair = CreateDisplayIdPair(new_display_info_list[0].id(),
+                                             new_display_info_list[1].id());
+    DisplayLayout layout = layout_store_->GetRegisteredDisplayLayout(pair);
+    current_default_multi_display_mode_ =
+        (layout.default_unified && unified_desktop_enabled_) ? UNIFIED
+                                                             : EXTENDED;
+  }
+
   if (multi_display_mode_ != MIRRORING)
-    multi_display_mode_ = default_multi_display_mode_;
+    multi_display_mode_ = current_default_multi_display_mode_;
 
   CreateSoftwareMirroringDisplayInfo(&new_display_info_list);
 
@@ -871,6 +876,11 @@ bool DisplayManager::IsInMirrorMode() const {
   return mirroring_display_id_ != gfx::Display::kInvalidDisplayID;
 }
 
+void DisplayManager::SetUnifiedDesktopEnabled(bool enable) {
+  unified_desktop_enabled_ = enable;
+  ReconfigureDisplays();
+}
+
 bool DisplayManager::IsInUnifiedMode() const {
   return multi_display_mode_ == UNIFIED &&
          !software_mirroring_display_list_.empty();
@@ -925,7 +935,8 @@ void DisplayManager::SetMirrorMode(bool mirror) {
     Shell::GetInstance()->display_configurator()->SetDisplayMode(new_state);
     return;
   }
-  multi_display_mode_ = mirror ? MIRRORING : default_multi_display_mode_;
+  multi_display_mode_ =
+      mirror ? MIRRORING : current_default_multi_display_mode_;
   ReconfigureDisplays();
   if (Shell::GetInstance()->display_configurator_animation()) {
     Shell::GetInstance()->display_configurator_animation()->
@@ -975,7 +986,8 @@ void DisplayManager::ToggleDisplayScaleFactor() {
 
 #if defined(OS_CHROMEOS)
 void DisplayManager::SetSoftwareMirroring(bool enabled) {
-  SetMultiDisplayMode(enabled ? MIRRORING : default_multi_display_mode_);
+  SetMultiDisplayMode(enabled ? MIRRORING
+                              : current_default_multi_display_mode_);
 }
 
 bool DisplayManager::SoftwareMirroringEnabled() const {
@@ -983,17 +995,20 @@ bool DisplayManager::SoftwareMirroringEnabled() const {
 }
 #endif
 
+void DisplayManager::SetDefaultMultiDisplayModeForCurrentDisplays(
+    MultiDisplayMode mode) {
+  DCHECK_NE(MIRRORING, mode);
+  DisplayIdPair pair = GetCurrentDisplayIdPair();
+  layout_store_->UpdateMultiDisplayState(pair, IsInMirrorMode(),
+                                         mode == UNIFIED);
+}
+
 void DisplayManager::SetMultiDisplayMode(MultiDisplayMode mode) {
   multi_display_mode_ = mode;
   mirroring_display_id_ = gfx::Display::kInvalidDisplayID;
   software_mirroring_display_list_.clear();
 }
 
-void DisplayManager::SetDefaultMultiDisplayMode(MultiDisplayMode mode) {
-  DCHECK_NE(mode, MIRRORING);
-  default_multi_display_mode_ = mode;
-}
-
 void DisplayManager::ReconfigureDisplays() {
   DisplayInfoList display_info_list;
   for (DisplayList::const_iterator iter = active_display_list_.begin();
diff --git a/ash/display/display_manager.h b/ash/display/display_manager.h
index 481310b..fa5cccf 100644
--- a/ash/display/display_manager.h
+++ b/ash/display/display_manager.h
@@ -250,6 +250,12 @@ class ASH_EXPORT DisplayManager
   const DisplayList& software_mirroring_display_list() const {
     return software_mirroring_display_list_;
   }
+
+  // Sets/gets if the unified desktop feature is enabled.
+  void SetUnifiedDesktopEnabled(bool enabled);
+  bool unified_desktop_enabled() const { return unified_desktop_enabled_; }
+
+  // Returns true if it's in unified desktop mode.
   bool IsInUnifiedMode() const;
 
   // Returns the display used for software mirrroring. Returns invalid
@@ -282,15 +288,15 @@ class ASH_EXPORT DisplayManager
   bool SoftwareMirroringEnabled() const override;
 #endif
 
-  // Sets/gets multi display mode.
-  void SetMultiDisplayMode(MultiDisplayMode mode);
-
   // Sets/gets default multi display mode.
-  void SetDefaultMultiDisplayMode(MultiDisplayMode mode);
-  MultiDisplayMode default_multi_display_mode() const {
-    return default_multi_display_mode_;
+  void SetDefaultMultiDisplayModeForCurrentDisplays(MultiDisplayMode mode);
+  MultiDisplayMode current_default_multi_display_mode() const {
+    return current_default_multi_display_mode_;
   }
 
+  // Sets multi display mode.
+  void SetMultiDisplayMode(MultiDisplayMode mode);
+
   // Reconfigure display configuration using the same
   // physical display. TODO(oshima): Refactor and move this
   // impl to |SetDefaultMultiDisplayMode|.
@@ -421,7 +427,7 @@ private:
   bool change_display_upon_host_resize_;
 
   MultiDisplayMode multi_display_mode_;
-  MultiDisplayMode default_multi_display_mode_;
+  MultiDisplayMode current_default_multi_display_mode_;
 
   int64 mirroring_display_id_;
   DisplayList software_mirroring_display_list_;
@@ -432,6 +438,8 @@ private:
   // User preference for the rotation of the internal display.
   gfx::Display::Rotation registered_internal_display_rotation_;
 
+  bool unified_desktop_enabled_;
+
   base::WeakPtrFactory<DisplayManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayManager);
diff --git a/ash/display/display_manager_unittest.cc b/ash/display/display_manager_unittest.cc
index e3c05e4..822452e 100644
--- a/ash/display/display_manager_unittest.cc
+++ b/ash/display/display_manager_unittest.cc
@@ -658,7 +658,7 @@ TEST_F(DisplayManagerTest, DisplayAddRemoveAtTheSameTime) {
   DisplayInfo secondary_info = display_manager()->GetDisplayInfo(secondary_id);
 
   // An id which is different from primary and secondary.
-  const int64 third_id = primary_id + secondary_id;
+  const int64 third_id = secondary_id + 1;
 
   DisplayInfo third_info =
       CreateDisplayInfo(third_id, gfx::Rect(0, 0, 600, 600));
@@ -1120,13 +1120,11 @@ TEST_F(DisplayManagerTest, Use125DSFForUIScaling) {
 TEST_F(DisplayManagerTest, ResolutionChangeInUnifiedMode) {
   if (!SupportsMultipleDisplays())
     return;
-
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
-
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
 
   DisplayManager* display_manager = Shell::GetInstance()->display_manager();
+  display_manager->SetUnifiedDesktopEnabled(true);
 
   UpdateDisplay("200x200, 400x400");
 
@@ -1520,13 +1518,15 @@ TEST_F(DisplayManagerTest, MAYBE_UpdateDisplayWithHostOrigin) {
 TEST_F(DisplayManagerTest, UnifiedDesktopBasic) {
   if (!SupportsMultipleDisplays())
     return;
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
 
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
 
   UpdateDisplay("400x500,300x200");
 
+  // Enable after extended mode.
+  display_manager()->SetUnifiedDesktopEnabled(true);
+
   // Defaults to the unified desktop.
   gfx::Screen* screen =
       gfx::Screen::GetScreenByType(gfx::SCREEN_TYPE_ALTERNATE);
@@ -1562,19 +1562,35 @@ TEST_F(DisplayManagerTest, UnifiedDesktopBasic) {
   }
 
   // Switch back to extended desktop.
-  display_manager()->SetDefaultMultiDisplayMode(DisplayManager::EXTENDED);
-  display_manager()->ReconfigureDisplays();
+  display_manager()->SetUnifiedDesktopEnabled(false);
   EXPECT_EQ("500x300", screen->GetPrimaryDisplay().size().ToString());
   EXPECT_EQ("400x500", ScreenUtil::GetSecondaryDisplay().size().ToString());
 }
 
+TEST_F(DisplayManagerTest, UnifiedDesktopEnabledWithExtended) {
+  if (!SupportsMultipleDisplays())
+    return;
+  // Don't check root window destruction in unified mode.
+  Shell::GetPrimaryRootWindow()->RemoveObserver(this);
+
+  UpdateDisplay("400x500,300x200");
+  DisplayIdPair pair = display_manager()->GetCurrentDisplayIdPair();
+  DisplayLayout layout =
+      display_manager()->layout_store()->GetRegisteredDisplayLayout(pair);
+  layout.default_unified = false;
+  display_manager()->layout_store()->RegisterLayoutForDisplayIdPair(
+      pair.first, pair.second, layout);
+  display_manager()->SetUnifiedDesktopEnabled(true);
+  EXPECT_FALSE(display_manager()->IsInUnifiedMode());
+}
+
 TEST_F(DisplayManagerTest, UnifiedDesktopWith2xDSF) {
   if (!SupportsMultipleDisplays())
     return;
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
 
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+  display_manager()->SetUnifiedDesktopEnabled(true);
   gfx::Screen* screen =
       gfx::Screen::GetScreenByType(gfx::SCREEN_TYPE_ALTERNATE);
 
@@ -1690,7 +1706,7 @@ TEST_F(DisplayManagerTest, ConfigureUnifiedTwice) {
 TEST_F(DisplayManagerTest, NoRotateUnifiedDesktop) {
   if (!SupportsMultipleDisplays())
     return;
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+  display_manager()->SetUnifiedDesktopEnabled(true);
 
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
@@ -1717,7 +1733,7 @@ TEST_F(DisplayManagerTest, NoRotateUnifiedDesktop) {
 TEST_F(DisplayManagerTest, UnifiedWithDockWindows) {
   if (!SupportsMultipleDisplays())
     return;
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+  display_manager()->SetUnifiedDesktopEnabled(true);
 
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
diff --git a/ash/display/display_util.cc b/ash/display/display_util.cc
index 5219dad..291b9a3 100644
--- a/ash/display/display_util.cc
+++ b/ash/display/display_util.cc
@@ -339,15 +339,19 @@ int FindDisplayIndexContainingPoint(const std::vector<gfx::Display>& displays,
 }
 
 DisplayIdPair CreateDisplayIdPair(int64 id1, int64 id2) {
+  return CompareDisplayIds(id1, id2) ? std::make_pair(id1, id2)
+                                     : std::make_pair(id2, id1);
+}
+
+bool CompareDisplayIds(int64 id1, int64 id2) {
   DCHECK_NE(id1, id2);
   // Output index is stored in the first 8 bits. See GetDisplayIdFromEDID
   // in edid_parser.cc.
   int index_1 = id1 & 0xFF;
   int index_2 = id2 & 0xFF;
-  if (gfx::Display::IsInternalDisplayId(id2) || index_2 < index_1)
-    return std::make_pair(id2, id1);
-  else
-    return std::make_pair(id1, id2);
+  DCHECK_NE(index_1, index_2) << id1 << " and " << id2;
+  return gfx::Display::IsInternalDisplayId(id1) ||
+         (index_1 < index_2 && !gfx::Display::IsInternalDisplayId(id2));
 }
 
 }  // namespace ash
diff --git a/ash/display/display_util.h b/ash/display/display_util.h
index dd0784b..0e4dadf 100644
--- a/ash/display/display_util.h
+++ b/ash/display/display_util.h
@@ -87,11 +87,15 @@ ASH_EXPORT int FindDisplayIndexContainingPoint(
     const std::vector<gfx::Display>& displays,
     const gfx::Point& point_in_screen);
 
-// Creates the DisplayIdPair where ids are sorted in the following manner.
-// 1) ID for internal display comes first.
-// 2) If none of the ids are internal, sorted by the output index.
+// Creates the DisplayIdPair where ids are sorted using |CompareDisplayIds|
+// below.
 ASH_EXPORT DisplayIdPair CreateDisplayIdPair(int64 id1, int64 id2);
 
+// Returns true if one of following conditinos is met.
+// 1) id1 is internal.
+// 2) output index of id1 < output index of id2 and id2 isn't internal.
+ASH_EXPORT bool CompareDisplayIds(int64 id1, int64 id2);
+
 }  // namespace ash
 
 #endif  // ASH_DISPLAY_DISPLAY_UTIL_H_
diff --git a/ash/display/display_util_unittest.cc b/ash/display/display_util_unittest.cc
index 1bd3d8c..1dcd0c7 100644
--- a/ash/display/display_util_unittest.cc
+++ b/ash/display/display_util_unittest.cc
@@ -98,11 +98,27 @@ TEST_F(DisplayUtilTest, CreateDisplayIdPair) {
   pair = CreateDisplayIdPair(10, 100);
   EXPECT_EQ(10, pair.first);
   EXPECT_EQ(100, pair.second);
+  {
+    test::ScopedSetInternalDisplayId set_internal(100);
+    pair = CreateDisplayIdPair(10, 100);
+    EXPECT_EQ(100, pair.first);
+    EXPECT_EQ(10, pair.second);
 
-  test::ScopedSetInternalDisplayId set_internal(100);
-  pair = CreateDisplayIdPair(10, 100);
-  EXPECT_EQ(100, pair.first);
-  EXPECT_EQ(10, pair.second);
+    pair = CreateDisplayIdPair(100, 10);
+    EXPECT_EQ(100, pair.first);
+    EXPECT_EQ(10, pair.second);
+  }
+
+  {
+    test::ScopedSetInternalDisplayId set_internal(10);
+    pair = CreateDisplayIdPair(10, 100);
+    EXPECT_EQ(10, pair.first);
+    EXPECT_EQ(100, pair.second);
+
+    pair = CreateDisplayIdPair(100, 10);
+    EXPECT_EQ(10, pair.first);
+    EXPECT_EQ(100, pair.second);
+  }
 }
 
 }  // namespace
diff --git a/ash/display/unified_mouse_warp_controller_unittest.cc b/ash/display/unified_mouse_warp_controller_unittest.cc
index 599d6ee..e176141 100644
--- a/ash/display/unified_mouse_warp_controller_unittest.cc
+++ b/ash/display/unified_mouse_warp_controller_unittest.cc
@@ -4,6 +4,7 @@
 
 #include "ash/display/unified_mouse_warp_controller.h"
 
+#include "ash/display/display_manager.h"
 #include "ash/display/mouse_cursor_event_filter.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
@@ -22,7 +23,7 @@ class UnifiedMouseWarpControllerTest : public test::AshTestBase {
 
   void SetUp() override {
     test::AshTestBase::SetUp();
-    test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+    Shell::GetInstance()->display_manager()->SetUnifiedDesktopEnabled(true);
   }
 
  protected:
diff --git a/ash/display/window_tree_host_manager.cc b/ash/display/window_tree_host_manager.cc
index f1e6aaf..77bec60 100644
--- a/ash/display/window_tree_host_manager.cc
+++ b/ash/display/window_tree_host_manager.cc
@@ -841,13 +841,11 @@ void WindowTreeHostManager::PostDisplayConfigurationChange() {
   DisplayLayoutStore* layout_store = display_manager->layout_store();
   if (display_manager->num_connected_displays() > 1) {
     DisplayIdPair pair = display_manager->GetCurrentDisplayIdPair();
+    DisplayLayout layout = layout_store->GetRegisteredDisplayLayout(pair);
     layout_store->UpdateMultiDisplayState(
-        pair, display_manager->IsInMirrorMode(),
-        display_manager->default_multi_display_mode() ==
-            DisplayManager::UNIFIED);
+        pair, display_manager->IsInMirrorMode(), layout.default_unified);
 
     if (Shell::GetScreen()->GetNumDisplays() > 1) {
-      DisplayLayout layout = layout_store->GetRegisteredDisplayLayout(pair);
       int64 primary_id = layout.primary_id;
       SetPrimaryDisplayId(primary_id == gfx::Display::kInvalidDisplayID
                               ? pair.first
diff --git a/ash/magnifier/magnification_controller_unittest.cc b/ash/magnifier/magnification_controller_unittest.cc
index 01a1e84..fcd7381 100644
--- a/ash/magnifier/magnification_controller_unittest.cc
+++ b/ash/magnifier/magnification_controller_unittest.cc
@@ -4,9 +4,9 @@
 
 #include "ash/magnifier/magnification_controller.h"
 
+#include "ash/display/display_manager.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
-#include "ash/test/display_manager_test_api.h"
 #include "base/strings/stringprintf.h"
 #include "ui/aura/env.h"
 #include "ui/aura/test/aura_test_utils.h"
@@ -670,7 +670,7 @@ TEST_F(MagnificationControllerTest, CenterTextCaretInViewport) {
 TEST_F(MagnificationControllerTest, EnableMagnifierInUnifiedDesktop) {
   if (!SupportsMultipleDisplays())
     return;
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+  Shell::GetInstance()->display_manager()->SetUnifiedDesktopEnabled(true);
 
   EXPECT_EQ(1.0f, GetMagnificationController()->GetScale());
 
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index 1953fed..97fd09e 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -173,8 +173,9 @@ void ReparentAllWindows(aura::Window* src, aura::Window* dst) {
       kContainerIdsToMove + arraysize(kContainerIdsToMove));
   // Check the default_multi_display_mode because this is also necessary
   // in trasition between mirror <-> unified mode.
-  if (Shell::GetInstance()->display_manager()->default_multi_display_mode() ==
-      DisplayManager::UNIFIED) {
+  if (Shell::GetInstance()
+          ->display_manager()
+          ->current_default_multi_display_mode() == DisplayManager::UNIFIED) {
     for (int id : kExtraContainerIdsToMoveInUnifiedMode)
       container_ids.push_back(id);
   }
diff --git a/ash/root_window_controller_unittest.cc b/ash/root_window_controller_unittest.cc
index 88e254f..923fdce 100644
--- a/ash/root_window_controller_unittest.cc
+++ b/ash/root_window_controller_unittest.cc
@@ -293,7 +293,7 @@ TEST_F(RootWindowControllerTest, MoveWindows_Modal) {
 TEST_F(RootWindowControllerTest, MoveWindows_LockWindowsInUnified) {
   if (!SupportsMultipleDisplays())
     return;
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+  Shell::GetInstance()->display_manager()->SetUnifiedDesktopEnabled(true);
 
   UpdateDisplay("500x500");
   const int kLockScreenWindowId = 1000;
diff --git a/ash/screen_util_unittest.cc b/ash/screen_util_unittest.cc
index 7fc9ae6..f8d7f33 100644
--- a/ash/screen_util_unittest.cc
+++ b/ash/screen_util_unittest.cc
@@ -117,11 +117,9 @@ TEST_F(ScreenUtilTest, ConvertRect) {
 TEST_F(ScreenUtilTest, ShelfDisplayBoundsInUnifiedDesktop) {
   if (!SupportsMultipleDisplays())
     return;
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
-
   DisplayManager* display_manager = Shell::GetInstance()->display_manager();
-  display_manager->SetDefaultMultiDisplayMode(DisplayManager::UNIFIED);
-  display_manager->SetMultiDisplayMode(DisplayManager::UNIFIED);
+
+  display_manager->SetUnifiedDesktopEnabled(true);
 
   views::Widget* widget = views::Widget::CreateWindowWithContextAndBounds(
       NULL, CurrentContext(), gfx::Rect(10, 10, 100, 100));
diff --git a/ash/shelf/shelf_layout_manager_unittest.cc b/ash/shelf/shelf_layout_manager_unittest.cc
index d447b06..7558b0c 100644
--- a/ash/shelf/shelf_layout_manager_unittest.cc
+++ b/ash/shelf/shelf_layout_manager_unittest.cc
@@ -2349,7 +2349,7 @@ TEST_F(ShelfLayoutManagerTest, ShutdownHandlesWindowActivation) {
 TEST_F(ShelfLayoutManagerTest, ShelfLayoutInUnifiedDesktop) {
   if (!SupportsMultipleDisplays())
     return;
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+  Shell::GetInstance()->display_manager()->SetUnifiedDesktopEnabled(true);
 
   UpdateDisplay("500x500, 500x500");
 
diff --git a/ash/system/chromeos/tray_display_unittest.cc b/ash/system/chromeos/tray_display_unittest.cc
index f6c205f..0a23260 100644
--- a/ash/system/chromeos/tray_display_unittest.cc
+++ b/ash/system/chromeos/tray_display_unittest.cc
@@ -315,9 +315,7 @@ TEST_F(TrayDisplayTest, InternalDisplayResized) {
   CheckAccessibleName();
 
   // Unified mode
-  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
-  display_manager->SetDefaultMultiDisplayMode(DisplayManager::UNIFIED);
-  display_manager->SetMultiDisplayMode(DisplayManager::UNIFIED);
+  display_manager->SetUnifiedDesktopEnabled(true);
   UpdateDisplay("300x200,400x500");
   // Update the cache variables as the primary root window changed.
   GetTray()->ShowDefaultView(BUBBLE_USE_EXISTING);
diff --git a/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc b/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc
index 6601dca..f487c75 100644
--- a/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc
+++ b/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc
@@ -276,8 +276,7 @@ TEST_F(AshPopupAlignmentDelegateTest, Unified) {
   if (!SupportsMultipleDisplays())
     return;
   DisplayManager* display_manager = Shell::GetInstance()->display_manager();
-  display_manager->SetDefaultMultiDisplayMode(DisplayManager::UNIFIED);
-  display_manager->SetMultiDisplayMode(DisplayManager::UNIFIED);
+  display_manager->SetUnifiedDesktopEnabled(true);
 
   // Reset the delegate as the primary display's shelf will be destroyed during
   // transition.
diff --git a/ash/test/display_manager_test_api.cc b/ash/test/display_manager_test_api.cc
index 434c7a9..73fb2d8 100644
--- a/ash/test/display_manager_test_api.cc
+++ b/ash/test/display_manager_test_api.cc
@@ -95,18 +95,6 @@ bool DisplayManagerTestApi::TestIfMouseWarpsAt(
   }
 }
 
-// static
-void DisplayManagerTestApi::EnableUnifiedDesktopForTest() {
-#if defined(OS_CHROMEOS)
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kAshEnableUnifiedDesktop);
-  Shell::GetInstance()
-      ->display_manager()
-      ->layout_store()
-      ->SetDefaultDisplayLayout(DisplayLayout());
-#endif
-}
-
 DisplayManagerTestApi::DisplayManagerTestApi()
     : display_manager_(Shell::GetInstance()->display_manager()) {}
 
diff --git a/ash/test/display_manager_test_api.h b/ash/test/display_manager_test_api.h
index b73e65d8..4bb070d 100644
--- a/ash/test/display_manager_test_api.h
+++ b/ash/test/display_manager_test_api.h
@@ -34,8 +34,6 @@ class DisplayManagerTestApi {
   static bool TestIfMouseWarpsAt(ui::test::EventGenerator& event_generator,
                                  const gfx::Point& point_in_screen);
 
-  static void EnableUnifiedDesktopForTest();
-
   DisplayManagerTestApi();
   virtual ~DisplayManagerTestApi();
 
diff --git a/chrome/browser/chromeos/display/display_preferences_unittest.cc b/chrome/browser/chromeos/display/display_preferences_unittest.cc
index eb065ad..07c0514 100644
--- a/chrome/browser/chromeos/display/display_preferences_unittest.cc
+++ b/chrome/browser/chromeos/display/display_preferences_unittest.cc
@@ -876,11 +876,11 @@ TEST_F(DisplayPreferencesTest, RotationLockTriggersStore) {
 }
 
 TEST_F(DisplayPreferencesTest, SaveUnifiedMode) {
-  ash::test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
 
   LoggedInAsUser();
   ash::DisplayManager* display_manager =
       ash::Shell::GetInstance()->display_manager();
+  display_manager->SetUnifiedDesktopEnabled(true);
 
   UpdateDisplay("200x200,100x100");
   ash::DisplayIdPair pair = display_manager->GetCurrentDisplayIdPair();
@@ -928,7 +928,8 @@ TEST_F(DisplayPreferencesTest, SaveUnifiedMode) {
   EXPECT_FALSE(stored_layout.mirrored);
 
   // Exit unified mode.
-  display_manager->SetDefaultMultiDisplayMode(ash::DisplayManager::EXTENDED);
+  display_manager->SetDefaultMultiDisplayModeForCurrentDisplays(
+      ash::DisplayManager::EXTENDED);
   display_manager->ReconfigureDisplays();
   ASSERT_TRUE(
       secondary_displays->GetDictionary(ToPairString(pair), &new_value));
@@ -953,7 +954,7 @@ TEST_F(DisplayPreferencesTest, RestoreUnifiedMode) {
   EXPECT_FALSE(display_manager->IsInUnifiedMode());
 
   // Restored to unified.
-  ash::test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+  display_manager->SetUnifiedDesktopEnabled(true);
   StoreDisplayBoolPropertyForPair(pair, "default_unified", true);
   LoadDisplayPreferences(false);
   UpdateDisplay("100x100,200x200");
diff --git a/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc b/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc
index 4859235..4fc8e39 100644
--- a/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc
+++ b/chrome/browser/ui/webui/options/chromeos/display_options_handler.cc
@@ -6,7 +6,6 @@
 
 #include <string>
 
-#include "ash/ash_switches.h"
 #include "ash/display/display_configurator_animation.h"
 #include "ash/display/display_manager.h"
 #include "ash/display/resolution_notification_controller.h"
@@ -331,7 +330,7 @@ void DisplayOptionsHandler::SendDisplayInfo(
 
 void DisplayOptionsHandler::UpdateDisplaySettingsEnabled() {
   bool enabled = GetDisplayManager()->num_connected_displays() <= 2;
-  bool show_unified_desktop = ash::switches::UnifiedDesktopEnabled();
+  bool show_unified_desktop = GetDisplayManager()->unified_desktop_enabled();
 
   web_ui()->CallJavascriptFunction(
       "options.BrowserOptions.enableDisplaySettings",
@@ -488,10 +487,10 @@ void DisplayOptionsHandler::HandleSetColorProfile(const base::ListValue* args) {
 
 void DisplayOptionsHandler::HandleSetUnifiedDesktopEnabled(
     const base::ListValue* args) {
-  DCHECK(ash::switches::UnifiedDesktopEnabled());
+  DCHECK(GetDisplayManager()->unified_desktop_enabled());
   bool enable = false;
   if (args->GetBoolean(0, &enable)) {
-    GetDisplayManager()->SetDefaultMultiDisplayMode(
+    GetDisplayManager()->SetDefaultMultiDisplayModeForCurrentDisplays(
         enable ? DisplayManager::UNIFIED : DisplayManager::EXTENDED);
     GetDisplayManager()->ReconfigureDisplays();
   }