Make the lifetime of wallpaper manager more clear.

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

 // Copyright 2014 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 <cstdlib>
 #include <cstring>
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/desktop_background/desktop_background_controller_observer.h"
 #include "ash/shell.h"
@@ skipping 29 matching lines @@
  public:
   WallpaperManagerCacheTest()
       : fake_user_manager_(new FakeChromeUserManager()),
         scoped_user_manager_(fake_user_manager_) {}
 
  protected:
   ~WallpaperManagerCacheTest() override {}
 
   FakeChromeUserManager* fake_user_manager() { return fake_user_manager_; }
 
-  void SetUp() override { test::AshTestBase::SetUp(); }
+  void SetUp() override {
+    test::AshTestBase::SetUp();
+    WallpaperManager::Initialize();
+  }
+
+  void TearDown() override {
+    WallpaperManager::Shutdown();
+    test::AshTestBase::TearDown();
+  }
 
   // Creates a test image of size 1x1.
   gfx::ImageSkia CreateTestImage(SkColor color) {
     SkBitmap bitmap;
     bitmap.allocN32Pixels(1, 1);
     bitmap.eraseColor(color);
     return gfx::ImageSkia::CreateFrom1xBitmap(bitmap);
   }
 
  private:
@@ skipping 40 matching lines @@
   EXPECT_TRUE(test_api->GetPathFromCache(test_user_2, &path));
   EXPECT_TRUE(cached_wallpaper.BackedBySameObjectAs(test_user_2_wallpaper));
   EXPECT_EQ(path, path2);
 
   // Not logged in user's wallpaper cache should be cleared.
   EXPECT_FALSE(test_api->GetWallpaperFromCache(test_user_3, &cached_wallpaper));
   EXPECT_FALSE(test_api->GetPathFromCache(test_user_3, &path));
 }
 
 }  // namespace chromeos