Refactor backdrop that is currently used in the maximized mode.

ash/wm/workspace/workspace_layout_manager.cc

Index: ash/wm/workspace/workspace_layout_manager.cc
diff --git a/ash/wm/workspace/workspace_layout_manager.cc b/ash/wm/workspace/workspace_layout_manager.cc
index 4da7bbc049739d96ae3c4196d9c96edd4dcdedd2..8ec5067b4757275fa1dff92d4936f31f31979088 100644
--- a/ash/wm/workspace/workspace_layout_manager.cc
+++ b/ash/wm/workspace/workspace_layout_manager.cc
@@ -22,7 +22,8 @@
 #include "ash/wm/window_state_aura.h"
 #include "ash/wm/window_util.h"
 #include "ash/wm/wm_event.h"
-#include "ash/wm/workspace/workspace_layout_manager_backdrop_delegate.h"
+#include "ash/wm/workspace/backdrop_controller.h"
+#include "ash/wm/workspace/backdrop_delegate.h"
 #include "ash/wm_window.h"
 #include "base/command_line.h"
 #include "ui/aura/client/aura_constants.h"
@@ -50,6 +51,7 @@ WorkspaceLayoutManager::WorkspaceLayoutManager(aura::Window* window)
   root_window_->AddObserver(this);
   display::Screen::GetScreen()->AddObserver(this);
   DCHECK(window->GetProperty(kSnapChildrenToPixelBoundary));
+  backdrop_controller_ = base::MakeUnique<BackdropController>(window_);
 }
 
 WorkspaceLayoutManager::~WorkspaceLayoutManager() {
@@ -65,9 +67,9 @@ WorkspaceLayoutManager::~WorkspaceLayoutManager() {
   Shell::Get()->RemoveShellObserver(this);
 }
 
-void WorkspaceLayoutManager::SetMaximizeBackdropDelegate(
-    std::unique_ptr<WorkspaceLayoutManagerBackdropDelegate> delegate) {
-  backdrop_delegate_ = std::move(delegate);
+void WorkspaceLayoutManager::SetBackdropDelegate(
+    std::unique_ptr<BackdropDelegate> delegate) {
+  backdrop_controller_->SetBackdropDelegate(std::move(delegate));
 }
 
 //////////////////////////////////////////////////////////////////////////////
@@ -84,8 +86,8 @@ void WorkspaceLayoutManager::OnWindowAddedToLayout(aura::Window* child) {
   window_state->AddObserver(this);
   UpdateShelfVisibility();
   UpdateFullscreenState();
-  if (backdrop_delegate_)
-    backdrop_delegate_->OnWindowAddedToLayout(WmWindow::Get(child));
+
+  backdrop_controller_->OnWindowAddedToLayout(child);
   WindowPositioner::RearrangeVisibleWindowOnShow(WmWindow::Get(child));
   if (Shell::Get()->screen_pinning_controller()->IsPinned())
     wm::GetWindowState(child)->DisableAlwaysOnTop(nullptr);
@@ -104,8 +106,7 @@ void WorkspaceLayoutManager::OnWillRemoveWindowFromLayout(aura::Window* child) {
 void WorkspaceLayoutManager::OnWindowRemovedFromLayout(aura::Window* child) {
   UpdateShelfVisibility();
   UpdateFullscreenState();
-  if (backdrop_delegate_)
-    backdrop_delegate_->OnWindowRemovedFromLayout(WmWindow::Get(child));
+  backdrop_controller_->OnWindowRemovedFromLayout(child);
 }
 
 void WorkspaceLayoutManager::OnChildWindowVisibilityChanged(aura::Window* child,
@@ -122,10 +123,7 @@ void WorkspaceLayoutManager::OnChildWindowVisibilityChanged(aura::Window* child,
         WmWindow::Get(child));
   UpdateFullscreenState();
   UpdateShelfVisibility();
-  if (backdrop_delegate_) {
-    backdrop_delegate_->OnChildWindowVisibilityChanged(WmWindow::Get(child),
-                                                       visible);
-  }
+  backdrop_controller_->OnChildWindowVisibilityChanged(child, visible);
 }
 
 void WorkspaceLayoutManager::SetChildBounds(aura::Window* child,
@@ -216,22 +214,24 @@ void WorkspaceLayoutManager::OnWindowHierarchyChanged(
 void WorkspaceLayoutManager::OnWindowPropertyChanged(aura::Window* window,
                                                      const void* key,
                                                      intptr_t old) {
-  if (key == aura::client::kAlwaysOnTopKey &&
-      window->GetProperty(aura::client::kAlwaysOnTopKey)) {
-    aura::Window* container =
-        root_window_controller_->always_on_top_controller()
-            ->GetContainer(WmWindow::Get(window))
-            ->aura_window();
-    if (window->parent() != container)
-      container->AddChild(window);
+  if (key == aura::client::kAlwaysOnTopKey) {
+    if (window->GetProperty(aura::client::kAlwaysOnTopKey)) {
+      aura::Window* container =
+          root_window_controller_->always_on_top_controller()
+              ->GetContainer(WmWindow::Get(window))
+              ->aura_window();
+      if (window->parent() != container)
+        container->AddChild(window);
+    }
+  } else if (key == aura::client::kHasBackdrop) {
+    backdrop_controller_->UpdateBackdrop();
   }
 }
 
 void WorkspaceLayoutManager::OnWindowStackingChanged(aura::Window* window) {
   UpdateShelfVisibility();
   UpdateFullscreenState();
-  if (backdrop_delegate_)
-    backdrop_delegate_->OnWindowStackingChanged(WmWindow::Get(window));
+  backdrop_controller_->OnWindowStackingChanged(window);
 }
 
 void WorkspaceLayoutManager::OnWindowDestroying(aura::Window* window) {
@@ -282,8 +282,7 @@ void WorkspaceLayoutManager::OnPostWindowStateTypeChange(
   }
 
   UpdateShelfVisibility();
-  if (backdrop_delegate_)
-    backdrop_delegate_->OnPostWindowStateTypeChange(window_state, old_type);
+  backdrop_controller_->OnPostWindowStateTypeChange(window_state, old_type);
 }
 
 //////////////////////////////////////////////////////////////////////////////