Extract colors from wallpaper and dynamically update login screen overlay

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

Index: chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
diff --git a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
index f4bbeb0ba300984c7aa8a19a81ef1a4877c3837b..8621f3677fe6f02e5de8a42746d601f3f7e9dcc0 100644
--- a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
+++ b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
@@ -204,6 +204,7 @@ void SetKnownUserWallpaperFilesId(
 // A helper to set the wallpaper image for Classic Ash and Mash.
 void SetWallpaper(const gfx::ImageSkia& image,
                   wallpaper::WallpaperLayout layout) {
+  WallpaperManager::Get()->CalculateProminentColor(image);
   if (ash_util::IsRunningInMash()) {
     // In mash, connect to the WallpaperController interface via mojo.
     service_manager::Connector* connector =
@@ -395,6 +396,10 @@ class WallpaperManager::PendingWallpaper :
 WallpaperManager::~WallpaperManager() {
   show_user_name_on_signin_subscription_.reset();
   device_wallpaper_image_subscription_.reset();
+  if (color_calculator_) {
+    color_calculator_->RemoveObserver(this);
+    color_calculator_.reset();
+  }
   user_manager::UserManager::Get()->RemoveSessionStateObserver(this);
   weak_factory_.InvalidateWeakPtrs();
 }
@@ -418,6 +423,11 @@ void WallpaperManager::Shutdown() {
   wallpaper_manager = nullptr;
 }
 
+// static
+bool WallpaperManager::HasInstance() {
+  return wallpaper_manager != nullptr;
+}
+
 bool WallpaperManager::IsPendingWallpaper(uint32_t image_id) {
   for (size_t i = 0; i < loading_.size(); ++i) {
     if (loading_[i]->GetImageId() == image_id) {
@@ -427,6 +437,28 @@ bool WallpaperManager::IsPendingWallpaper(uint32_t image_id) {
   return false;
 }
 
+void WallpaperManager::CalculateProminentColor(const gfx::ImageSkia& image) {
+  // Cancel in-flight color calculations, if any.
+  if (color_calculator_) {
+    color_calculator_->RemoveObserver(this);
+    color_calculator_.reset();
+  }
+
+  color_calculator_ = base::MakeUnique<wallpaper::WallpaperColorCalculator>(
+      image, color_utils::LumaRange::DARK, color_utils::SaturationRange::MUTED,
+      task_runner_);
+  color_calculator_->AddObserver(this);
+  if (!color_calculator_->StartCalculation()) {
+    color_calculator_->RemoveObserver(this);
+    color_calculator_.reset();
+    if (!prominent_color_.has_value())
+      return;
+    prominent_color_.reset();
+    for (auto& observer : observers_)
+      observer.OnWallpaperColorsChanged();
+  }
+}
+
 WallpaperManager::WallpaperResolution
 WallpaperManager::GetAppropriateResolution() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
@@ -911,6 +943,18 @@ void WallpaperManager::OnWindowDestroying(aura::Window* window) {
       user_manager::UserManager::Get()->GetActiveUser()->username_hash());
 }
 
+void WallpaperManager::OnColorCalculationComplete() {
+  SkColor color = color_calculator_->prominent_color();
+  color_calculator_->RemoveObserver(this);
+  color_calculator_.reset();
+  if (prominent_color_ == color)
+    return;
+  prominent_color_ = color;
+
+  for (auto& observer : observers_)
+    observer.OnWallpaperColorsChanged();
+}
+
 // WallpaperManager, private: --------------------------------------------------
 
 WallpaperManager::WallpaperManager()