Replace single-threaded SequencedWorkerPool with base::Thread in WallpaperResizerTest.

Also while here:
 - const scoped_refptr<>& => scoped_refptr<> + std::move
   (helps avoiding unnecessary refcount bumps:
    https://groups.google.com/a/chromium.org/d/topic/chromium-dev/TlL1D-Djta0/discussion)

BUG=646443

Review-Url: https://codereview.chromium.org/2338363002
Cr-Commit-Position: refs/heads/master@{#418855}

components/wallpaper/wallpaper_resizer.cc

@@ -4,6 +4,8 @@
 
 #include "components/wallpaper/wallpaper_resizer.h"
 
+#include <utility>
+
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
@@ -105,12 +107,12 @@ WallpaperResizer::WallpaperResizer(
     const gfx::ImageSkia& image,
     const gfx::Size& target_size,
     WallpaperLayout layout,
-    const scoped_refptr<base::TaskRunner>& task_runner)
+    scoped_refptr<base::TaskRunner> task_runner)
     : image_(image),
       original_image_id_(GetImageId(image_)),
       target_size_(target_size),
       layout_(layout),
-      task_runner_(task_runner),
+      task_runner_(std::move(task_runner)),
       weak_ptr_factory_(this) {
   image_.MakeThreadSafe();
 }

components/wallpaper/wallpaper_resizer.h

@@ -38,7 +38,7 @@ class WALLPAPER_EXPORT WallpaperResizer {
   WallpaperResizer(const gfx::ImageSkia& image,
                    const gfx::Size& target_size,
                    WallpaperLayout layout,
-                   const scoped_refptr<base::TaskRunner>& task_runner);
+                   scoped_refptr<base::TaskRunner> task_runner);
 
   ~WallpaperResizer();
 

components/wallpaper/wallpaper_resizer_unittest.cc

@@ -11,7 +11,7 @@
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
-#include "base/test/sequenced_worker_pool_owner.h"
+#include "base/threading/thread.h"
 #include "components/wallpaper/wallpaper_resizer_observer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/image/image_skia_rep.h"
@@ -62,15 +62,19 @@ namespace wallpaper {
 class WallpaperResizerTest : public testing::Test,
                              public WallpaperResizerObserver {
  public:
-  WallpaperResizerTest() : worker_pool_owner_(1, "WallpaperResizerTest") {}
+  WallpaperResizerTest() : worker_thread_("WallpaperResizerTest") {}
   ~WallpaperResizerTest() override {}
 
+  void SetUp() override {
+    ASSERT_TRUE(worker_thread_.Start());
+  }
+
   gfx::ImageSkia Resize(const gfx::ImageSkia& image,
                         const gfx::Size& target_size,
                         WallpaperLayout layout) {
     std::unique_ptr<WallpaperResizer> resizer;
     resizer.reset(
-        new WallpaperResizer(image, target_size, layout, worker_pool()));
+        new WallpaperResizer(image, target_size, layout, task_runner()));
     resizer->AddObserver(this);
     resizer->StartResize();
     WaitForResize();
@@ -78,8 +82,8 @@ class WallpaperResizerTest : public testing::Test,
     return resizer->image();
   }
 
-  base::SequencedWorkerPool* worker_pool() {
-    return worker_pool_owner_.pool().get();
+  scoped_refptr<base::TaskRunner> task_runner() {
+    return worker_thread_.task_runner();
   }
 
   void WaitForResize() { base::RunLoop().Run(); }
@@ -88,7 +92,7 @@ class WallpaperResizerTest : public testing::Test,
 
  private:
   base::MessageLoop message_loop_;
-  base::SequencedWorkerPoolOwner worker_pool_owner_;
+  base::Thread worker_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperResizerTest);
 };
@@ -149,7 +153,7 @@ TEST_F(WallpaperResizerTest, ImageId) {
   // Create a WallpaperResizer and check that it reports an original image ID
   // both pre- and post-resize that matches the ID returned by GetImageId().
   WallpaperResizer resizer(image, gfx::Size(10, 20), WALLPAPER_LAYOUT_STRETCH,
-                           worker_pool());
+                           task_runner());
   EXPECT_EQ(WallpaperResizer::GetImageId(image), resizer.original_image_id());
   resizer.AddObserver(this);
   resizer.StartResize();