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..ffd961d7858e02ea5d6b1088bd002b3a37b9175c 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"
@@ -37,7 +39,8 @@ 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;
 
@@ -58,6 +61,13 @@ class WallpaperManager
   // 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);
+
+  SkColor prominent_color() const { return prominent_color_; }
+
   // wallpaper::WallpaperManagerBase:
   WallpaperResolution GetAppropriateResolution() override;
   void AddObservers() override;
@@ -113,6 +123,9 @@ class WallpaperManager
   // aura::WindowObserver:
   void OnWindowDestroying(aura::Window* window) override;
 
+  // wallpaper::WallpaperColorCalculatorObserver:
+  void OnColorCalculationComplete() override;
+
  private:
   friend class TestApi;
   friend class WallpaperManagerBrowserTest;
@@ -159,6 +172,9 @@ class WallpaperManager
       const AccountId& account_id,
       std::unique_ptr<user_manager::UserImage> user_image);
 
+  // Sets |prominent_color_| and notifies the observers if there is a change.
+  void SetProminentColor(SkColor color);
+
   // wallpaper::WallpaperManagerBase:
   void InitializeRegisteredDeviceWallpaper() override;
   bool GetUserWallpaperInfo(const AccountId& account_id,
@@ -238,6 +254,12 @@ class WallpaperManager
       activation_client_observer_;
   ScopedObserver<aura::Window, aura::WindowObserver> window_observer_;
 
+  // The prominent color extracted from the current wallpaper.
+  // SK_ColorTRANSPARENT is used if color extraction fails.

[jdufault, 2017/06/12 21:37:28]

Use base::Optional<>. Try to avoid using magic values for failure state, better
to encode it into the type system.

[Wenzhao (Colin) Zang, 2017/06/12 23:40:34]

Done.

+  SkColor prominent_color_;
+
+  std::unique_ptr<wallpaper::WallpaperColorCalculator> color_calculator_;
+
   base::WeakPtrFactory<WallpaperManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperManager);