Fix "modal isn't modal in multi displays" issue

ash/wm/system_modal_container_layout_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/wm/system_modal_container_layout_manager.h"
 
 #include <cmath>
 
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_window_ids.h"
@@ skipping 95 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // SystemModalContainerLayoutManager, Keyboard::KeybaordControllerObserver
 // implementation:
 
 void SystemModalContainerLayoutManager::OnKeyboardBoundsChanging(
     const gfx::Rect& new_bounds) {
   PositionDialogsAfterWorkAreaResize();
 }
 
-bool SystemModalContainerLayoutManager::CanWindowReceiveEvents(
+bool SystemModalContainerLayoutManager::IsActiveModalWindows(
     aura::Window* window) {
-  // We could get when we're at lock screen and there is modal window at
-  // system modal window layer which added event filter.
-  // Now this lock modal windows layer layout manager should not block events
-  // for windows at lock layer.
-  // See SystemModalContainerLayoutManagerTest.EventFocusContainers and
-  // http://crbug.com/157469
-  if (modal_windows_.empty())
-    return true;
-  // This container can not handle events if the screen is locked and it is not
-  // above the lock screen layer (crbug.com/110920).
-  if (Shell::GetInstance()->session_state_delegate()->IsUserSessionBlocked() &&
-      container_->id() < ash::kShellWindowId_LockScreenContainer)
-    return true;
-  return wm::GetActivatableWindow(window) == modal_window();
+  return modal_window() != nullptr &&

[James Cook, 2016/06/16 20:31:35]

For my knowledge: Do we now prefer comparing to nullptr vs. if (!pointer) and if
(pointer) ?

[oshima, 2016/06/17 00:06:12]

I saw the discussion but I haven't read to the conslusion. I'm happy to change,
so let me know

No, I don't think there is preference. Changed to !pointer to be consistent. (I
think UI code tends to prefer this, probably because it's shorter)

I've seen a recent discussion but I don't think there was any consensus on this.

[James Cook, 2016/06/17 16:04:43]

I prefer !pointer myself, just for consistency with old code.

(Out of curiosity, on which mailing list have you seen these discussions?
Chromium-dev?)

+         wm::GetActivatableWindow(window) == modal_window();
 }
 
 bool SystemModalContainerLayoutManager::ActivateNextModalWindow() {
   if (modal_windows_.empty())
     return false;
   wm::ActivateWindow(modal_window());
   return true;
 }
 
 void SystemModalContainerLayoutManager::CreateModalBackground() {
@@ skipping 111 matching lines @@
 bool SystemModalContainerLayoutManager::DialogIsCentered(
     const gfx::Rect& window_bounds) {
   gfx::Point window_center = window_bounds.CenterPoint();
   gfx::Point container_center = GetUsableDialogArea().CenterPoint();
   return
       std::abs(window_center.x() - container_center.x()) < kCenterPixelDelta &&
       std::abs(window_center.y() - container_center.y()) < kCenterPixelDelta;
 }
 
 }  // namespace ash