[ash-md] Updated the overflow shelf to change colors based on the wallpaper.

ash/test/wallpaper_controller_test_api.h

+// 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 "ash/ash_export.h"
+#include "base/macros.h"
+#include "third_party/skia/include/core/SkColor.h"
+
+namespace ash {
+
+class WallpaperController;
+
+namespace test {
+
+class ASH_EXPORT WallpaperControllerTestApi {
+ public:
+  explicit WallpaperControllerTestApi(WallpaperController* controller);
+  virtual ~WallpaperControllerTestApi();
+
+  // Creates and sets a new wallpaper that cause the prominent color of the
+  // |controller_| to be a valid (aka not kInvalidColor) color. The
+  // WallpaperControllerObservers should be notified as well. This is assumes
+  // the default DARK-MUTED luma-saturation ranges are in effect.
+  //
+  // The expected prominent color is returned.
+  SkColor ApplyColorProducingWallpaper();
+
+ private:
+  WallpaperController* controller_;
+
+  DISALLOW_COPY_AND_ASSIGN(WallpaperControllerTestApi);
+};
+
+}  // namespace test
+}  // namespace ash