This is reland of crrev.com/2884623002.

Added test uncovered a stack-use-after-scope issue in AshTouchExplorationManager. Patch #2 fixes the issue.

Refactor backdrop that is currently used in the maximized mode.

The maximized mode creates a backdrop window so that a user will not see the content of windows behind the top window,
in case it doesn't cover the entire window. (can happen if the maximize size is specified for example)
This CL generalizes the backdrop code used in maximize mode as to create the backdrop in the following scenarios:

1) Has a aura::client::kHasBackdrop property = true.
2) BackdropDelegate::HasBackdrop(aura::Window* window) returns true.
3) Active ARC window when the spoken feedback is enabled.

* Added delegate to check if the window should have a backdrop.
  Maximized mode always puts a backdrop.

* Added kHasBackdrop property for a window that needs a backdrop even in clamshell.

* Move the accessibility feature implemented in exo's backbround. This
  is useful and should be there even for non-arc/exo case.

TBR=jamescook@chromium.org,reveman@chromium.org,sky@chromium.org
BUG=721646
TEST=coverted by unit tests

Review-Url: https://codereview.chromium.org/2884623002
Cr-Commit-Position: refs/heads/master@{#472401}
Committed: https://chromium.googlesource.com/chromium/src/+/04936c54ed2396ae54cd824e24f11151e0e11948

patch from issue 2884623002 at patchset 220001 (http://crrev.com/2884623002#ps220001)

Review-Url: https://codereview.chromium.org/2890733005
Cr-Commit-Position: refs/heads/master@{#472479}

ash/BUILD.gn

@@ -658,6 +658,8 @@ component("ash") {
     "wm/lock_state_observer.h",
     "wm/lock_window_state.cc",
     "wm/lock_window_state.h",
+    "wm/maximize_mode/maximize_mode_backdrop_delegate_impl.cc",
+    "wm/maximize_mode/maximize_mode_backdrop_delegate_impl.h",
     "wm/maximize_mode/maximize_mode_controller.cc",
     "wm/maximize_mode/maximize_mode_controller.h",
     "wm/maximize_mode/maximize_mode_event_handler.cc",
@@ -673,8 +675,6 @@ component("ash") {
     "wm/maximize_mode/scoped_disable_internal_mouse_and_keyboard_ozone.h",
     "wm/maximize_mode/scoped_disable_internal_mouse_and_keyboard_x11.cc",
     "wm/maximize_mode/scoped_disable_internal_mouse_and_keyboard_x11.h",
-    "wm/maximize_mode/workspace_backdrop_delegate.cc",
-    "wm/maximize_mode/workspace_backdrop_delegate.h",
     "wm/mru_window_tracker.cc",
     "wm/mru_window_tracker.h",
     "wm/overlay_event_filter.cc",
@@ -794,6 +794,9 @@ component("ash") {
     "wm/wm_types.h",
     "wm/wm_window_animations.cc",
     "wm/wm_window_animations.h",
+    "wm/workspace/backdrop_controller.cc",
+    "wm/workspace/backdrop_controller.h",
+    "wm/workspace/backdrop_delegate.h",
     "wm/workspace/magnetism_matcher.cc",
     "wm/workspace/magnetism_matcher.h",
     "wm/workspace/multi_window_resize_controller.cc",
@@ -808,7 +811,6 @@ component("ash") {
     "wm/workspace/workspace_event_handler_aura.h",
     "wm/workspace/workspace_layout_manager.cc",
     "wm/workspace/workspace_layout_manager.h",
-    "wm/workspace/workspace_layout_manager_backdrop_delegate.h",
     "wm/workspace/workspace_types.h",
     "wm/workspace/workspace_window_resizer.cc",
     "wm/workspace/workspace_window_resizer.h",

ash/ash_touch_exploration_manager_chromeos.cc

@@ -167,9 +167,9 @@ void AshTouchExplorationManager::UpdateTouchExplorationState() {
               touch_accessibility_enabler_.get());
     }
     if (pass_through_surface) {
-      const gfx::Rect& work_area = root_window_controller_->GetWindow()
-                                       ->GetDisplayNearestWindow()
-                                       .work_area();
+      const gfx::Rect work_area = root_window_controller_->GetWindow()
+                                      ->GetDisplayNearestWindow()
+                                      .work_area();
       touch_exploration_controller_->SetExcludeBounds(work_area);
       SilenceSpokenFeedback();
       Shell::Get()->accessibility_delegate()->ClearFocusHighlight();

ash/test/workspace_controller_test_api.cc

@@ -5,6 +5,8 @@
 #include "ash/test/workspace_controller_test_api.h"
 
 #include "ash/test/workspace_event_handler_test_helper.h"
+#include "ash/wm/workspace/backdrop_controller.h"
+#include "ash/wm/workspace/workspace_layout_manager.h"
 #include "ash/wm/workspace_controller.h"
 #include "ui/aura/window.h"
 
@@ -26,5 +28,9 @@ WorkspaceControllerTestApi::GetMultiWindowResizeController() {
   return WorkspaceEventHandlerTestHelper(GetEventHandler()).resize_controller();
 }
 
+aura::Window* WorkspaceControllerTestApi::GetBackdropWindow() {
+  return controller_->layout_manager_->backdrop_controller_->backdrop_window_;
+}
+
 }  // namespace test
 }  // namespace ash

ash/test/workspace_controller_test_api.h

@@ -22,6 +22,7 @@ class ASH_EXPORT WorkspaceControllerTestApi {
 
   WorkspaceEventHandler* GetEventHandler();
   MultiWindowResizeController* GetMultiWindowResizeController();
+  aura::Window* GetBackdropWindow();
 
  private:
   WorkspaceController* controller_;

ash/wm/maximize_mode/maximize_mode_backdrop_delegate_impl.cc

@@ -0,0 +1,17 @@
+// Copyright 2017 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/maximize_mode/maximize_mode_backdrop_delegate_impl.h"
+
+namespace ash {
+
+MaximizeModeBackdropDelegateImpl::MaximizeModeBackdropDelegateImpl() = default;
+
+MaximizeModeBackdropDelegateImpl::~MaximizeModeBackdropDelegateImpl() = default;
+
+bool MaximizeModeBackdropDelegateImpl::HasBackdrop(aura::Window* window) {
+  return true;
+}
+
+}  // namespace ash

ash/wm/maximize_mode/maximize_mode_backdrop_delegate_impl.h

@@ -0,0 +1,27 @@
+// Copyright 2017 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/workspace/backdrop_delegate.h"
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+
+namespace ash {
+
+// A backdrop delegate for MaximizedMode, which always creates a backdrop.
+// This is also used in the WorkspaceLayoutManagerBackdropTest, hence
+// is public.
+class ASH_EXPORT MaximizeModeBackdropDelegateImpl : public BackdropDelegate {
+ public:
+  MaximizeModeBackdropDelegateImpl();
+  ~MaximizeModeBackdropDelegateImpl() override;
+
+ protected:
+  bool HasBackdrop(aura::Window* window) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MaximizeModeBackdropDelegateImpl);
+};
+
+}  // namespace ash

ash/wm/maximize_mode/maximize_mode_window_manager.cc

@@ -10,9 +10,9 @@
 #include "ash/session/session_state_delegate.h"
 #include "ash/shell.h"
 #include "ash/shell_port.h"
+#include "ash/wm/maximize_mode/maximize_mode_backdrop_delegate_impl.h"
 #include "ash/wm/maximize_mode/maximize_mode_event_handler.h"
 #include "ash/wm/maximize_mode/maximize_mode_window_state.h"
-#include "ash/wm/maximize_mode/workspace_backdrop_delegate.h"
 #include "ash/wm/mru_window_tracker.h"
 #include "ash/wm/overview/window_selector_controller.h"
 #include "ash/wm/window_state.h"
@@ -82,20 +82,10 @@ void MaximizeModeWindowManager::WindowStateDestroyed(WmWindow* window) {
 }
 
 void MaximizeModeWindowManager::OnOverviewModeStarting() {
-  if (backdrops_hidden_)
-    return;
-
-  EnableBackdropBehindTopWindowOnEachDisplay(false);
   SetDeferBoundsUpdates(true);
-  backdrops_hidden_ = true;
 }
 
 void MaximizeModeWindowManager::OnOverviewModeEnded() {
-  if (!backdrops_hidden_)
-    return;
-
-  backdrops_hidden_ = false;
-  EnableBackdropBehindTopWindowOnEachDisplay(true);
   SetDeferBoundsUpdates(false);
 }
 
@@ -202,8 +192,7 @@ void MaximizeModeWindowManager::SetIgnoreWmEventsForExit() {
   }
 }
 
-MaximizeModeWindowManager::MaximizeModeWindowManager()
-    : backdrops_hidden_(false) {
+MaximizeModeWindowManager::MaximizeModeWindowManager() {
   // The overview mode needs to be ended before the maximize mode is started. To
   // guarantee the proper order, it will be turned off from here.
   CancelOverview();
@@ -310,17 +299,12 @@ bool MaximizeModeWindowManager::IsContainerWindow(aura::Window* window) {
 
 void MaximizeModeWindowManager::EnableBackdropBehindTopWindowOnEachDisplay(
     bool enable) {
-  if (backdrops_hidden_)
-    return;
-
   // Inform the WorkspaceLayoutManager that we want to show a backdrop behind
   // the topmost window of its container.
   for (WmWindow* root : ShellPort::Get()->GetAllRootWindows()) {
     RootWindowController* controller = root->GetRootWindowController();
-    WmWindow* default_container =
-        root->GetChildByShellWindowId(kShellWindowId_DefaultContainer);
-    controller->workspace_controller()->SetMaximizeBackdropDelegate(
-        enable ? base::MakeUnique<WorkspaceBackdropDelegate>(default_container)
+    controller->workspace_controller()->SetBackdropDelegate(
+        enable ? base::MakeUnique<MaximizeModeBackdropDelegateImpl>()
                : nullptr);
   }
 }

ash/wm/maximize_mode/maximize_mode_window_manager.h

@@ -131,9 +131,6 @@ class ASH_EXPORT MaximizeModeWindowManager : public aura::WindowObserver,
   // Windows added to the container, but not yet shown.
   std::unordered_set<aura::Window*> added_windows_;
 
-  // True if all backdrops are hidden.
-  bool backdrops_hidden_;
-
   std::unique_ptr<wm::MaximizeModeEventHandler> event_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(MaximizeModeWindowManager);