Extract colors from wallpaper and dynamically update login screen overlay

chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h

Index: chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
diff --git a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
index cefafb3734460443239feb5ed5594c6acde51c75..d3962a8847f5de267afc7587e2c43c2e1ca5386c 100644
--- a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
+++ b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
@@ -19,6 +19,8 @@
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_image/user_image.h"
 #include "components/user_manager/user_manager.h"
+#include "components/wallpaper/wallpaper_color_calculator.h"
+#include "components/wallpaper/wallpaper_color_calculator_observer.h"
 #include "components/wallpaper/wallpaper_layout.h"
 #include "components/wallpaper/wallpaper_manager_base.h"
 #include "content/public/browser/notification_observer.h"
@@ -37,14 +39,14 @@ class WallpaperManager
       public content::NotificationObserver,
       public user_manager::UserManager::UserSessionStateObserver,
       public wm::ActivationChangeObserver,
-      public aura::WindowObserver {
+      public aura::WindowObserver,
+      public wallpaper::WallpaperColorCalculatorObserver {
  public:
   class PendingWallpaper;
 
   ~WallpaperManager() override;
 
-  // Creates an instance of Wallpaper Manager. If there is no instance, create
-  // one. Otherwise, returns the existing instance.
+  // Expects there is no instance of WallpaperManager and create one.
   static void Initialize();
 
   // Gets pointer to singleton WallpaperManager instance.
@@ -54,10 +56,23 @@ class WallpaperManager
   // WallpaperManager to remove any observers it has registered.
   static void Shutdown();
 
+  // Checks whether the instance exists. In general, please refrain from using
+  // this function. Use Get() directly when needing to access the singleton.
+  // TODO(crbug.com/733709): Remove this function when color calculation for
+  // login screen is moved elsewhere.
+  static bool HasInstance();
+
   // Returns if the image is in the pending list. |image_id| can be obtained
   // from gfx::ImageSkia by using WallpaperResizer::GetImageId().
   bool IsPendingWallpaper(uint32_t image_id);
 
+  // Calculates a prominent color based on the wallpaper image and notifies
+  // |observers_| of the value. An existing calculation in progress (if any)
+  // will be destroyed first.
+  void CalculateProminentColor(const gfx::ImageSkia& image);
+
+  base::Optional<SkColor> prominent_color() const { return prominent_color_; }
+
   // wallpaper::WallpaperManagerBase:
   WallpaperResolution GetAppropriateResolution() override;
   void AddObservers() override;
@@ -113,6 +128,9 @@ class WallpaperManager
   // aura::WindowObserver:
   void OnWindowDestroying(aura::Window* window) override;
 
+  // wallpaper::WallpaperColorCalculatorObserver:
+  void OnColorCalculationComplete() override;
+
  private:
   friend class TestApi;
   friend class WallpaperManagerBrowserTest;
@@ -238,6 +256,14 @@ class WallpaperManager
       activation_client_observer_;
   ScopedObserver<aura::Window, aura::WindowObserver> window_observer_;
 
+  // The prominent color extracted from the current wallpaper. It doesn't have
+  // value if color extraction fails.
+  base::Optional<SkColor> prominent_color_;
+
+  // TODO(crbug.com/733709): Remove color calculation here when the old signin
+  // screen implementation is deprecated.
+  std::unique_ptr<wallpaper::WallpaperColorCalculator> color_calculator_;
+
   base::WeakPtrFactory<WallpaperManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperManager);