[ash-md] Wired in the Shelf color to be derived from the Wallpaper.

components/wallpaper/wallpaper_color_calculator.cc

+// 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 "components/wallpaper/wallpaper_color_calculator.h"
+
+#include <string>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/task_runner.h"
+#include "base/task_runner_util.h"
+
+namespace wallpaper {
+
+WallpaperColorCalculator::WallpaperColorCalculator(
+    const gfx::ImageSkia& image,
+    color_utils::LumaRange luma,
+    color_utils::SaturationRange saturation,
+    scoped_refptr<base::TaskRunner> task_runner)
+    : image_(image),
+      luma_(luma),
+      saturation_(saturation),
+      task_runner_(std::move(task_runner)),
+      weak_ptr_factory_(this) {}
+
+WallpaperColorCalculator::~WallpaperColorCalculator() {}
+
+void WallpaperColorCalculator::AddObserver(
+    WallpaperColorCalculatorObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void WallpaperColorCalculator::RemoveObserver(
+    WallpaperColorCalculatorObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+bool WallpaperColorCalculator::StartCalculation() {
+  image_.MakeThreadSafe();
+  if (base::PostTaskAndReplyWithResult(
+          task_runner_.get(), FROM_HERE,
+          base::Bind(&color_utils::CalculateProminentColorOfBitmap,
+                     *image_.bitmap(), luma_, saturation_),
+          base::Bind(&WallpaperColorCalculator::NotifyCalculationComplete,
+                     weak_ptr_factory_.GetWeakPtr()))) {
+    return true;
+  }
+
+  LOG(WARNING) << "PostSequencedWorkerTask failed. "
+               << "Wallpaper promiment color may not be calculated.";
+
+  prominent_color_ = SK_ColorTRANSPARENT;
+  return false;
+}
+
+void WallpaperColorCalculator::SetTaskRunnerForTest(
+    scoped_refptr<base::TaskRunner> task_runner) {
+  task_runner_ = task_runner;
+}
+
+void WallpaperColorCalculator::NotifyCalculationComplete(
+    SkColor prominent_color) {
+  prominent_color_ = prominent_color;
+  for (auto& observer : observers_)
+    observer.OnColorCalculationComplete();
+}
+
+}  // namespace wallpaper