arc: Do not keep track of in-flight decode requests.

chrome/browser/chromeos/arc/arc_wallpaper_handler.cc

 // Copyright 2016 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 "chrome/browser/chromeos/arc/arc_wallpaper_handler.h"
 
 #include <string>
 #include <vector>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h"
-#include "chrome/browser/image_decoder.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "components/user_manager/user_manager.h"
 #include "components/wallpaper/wallpaper_files_id.h"
 #include "components/wallpaper/wallpaper_layout.h"
 #include "content/public/browser/browser_thread.h"
 #include "ui/gfx/image/image_skia.h"
 
 using user_manager::UserManager;
 
 namespace arc {
@@ skipping 27 matching lines @@
       image, update_wallpaper);
 
   // TODO(crbug.com/618922): Register the wallpaper to Chrome OS wallpaper
   // picker. Currently the new wallpaper does not appear there. The best way to
   // make this happen seems to do the same things as wallpaper_api.cc and
   // wallpaper_private_api.cc.
 }
 
 }  // namespace
 
-// An implementation of ImageDecoder::ImageRequest that just calls back
-// ArcWallpaperHandler.
-class ArcWallpaperHandler::ImageRequestImpl
-    : public ImageDecoder::ImageRequest {
- public:
-  // |handler| outlives this instance.
-  explicit ImageRequestImpl(ArcWallpaperHandler* handler) : handler_(handler) {}
-
-  // ImageDecoder::ImageRequest implementation.
-  void OnImageDecoded(const SkBitmap& bitmap) override {
-    handler_->OnImageDecoded(this, bitmap);
-  }
-  void OnDecodeImageFailed() override { handler_->OnDecodeImageFailed(this); }
-
- private:
-  ArcWallpaperHandler* const handler_;
-
-  DISALLOW_COPY_AND_ASSIGN(ImageRequestImpl);
-};
-
 ArcWallpaperHandler::ArcWallpaperHandler() = default;
 
 ArcWallpaperHandler::~ArcWallpaperHandler() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  // Cancel in-flight requests.
-  for (auto& request : inflight_requests_)
-    ImageDecoder::Cancel(request.get());
-  inflight_requests_.clear();
+  // Make sure the callback is never called after destruction. It is safe to
+  // call Cancel() even when there is no in-flight request.
+  ImageDecoder::Cancel(this);
 }
 
 void ArcWallpaperHandler::SetWallpaper(const std::vector<uint8_t>& jpeg_data) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  std::unique_ptr<ImageRequestImpl> request =
-      base::MakeUnique<ImageRequestImpl>(this);
   // TODO(nya): Improve ImageDecoder to minimize copy.

[hidehiko, 2016/07/26 06:19:10]

As we chatted offline, to make the behavior slightly predictable, could you add
Cancel(this) here?

[Shuhei Takahashi, 2016/07/26 06:22:07]

Done.

   std::string jpeg_data_as_string(
       reinterpret_cast<const char*>(jpeg_data.data()), jpeg_data.size());
-  ImageDecoder::StartWithOptions(request.get(), jpeg_data_as_string,
+  ImageDecoder::StartWithOptions(this, jpeg_data_as_string,
                                  ImageDecoder::ROBUST_JPEG_CODEC, true);
-  inflight_requests_.insert(std::move(request));
 }
 
-void ArcWallpaperHandler::OnImageDecoded(ImageRequestImpl* request,
-                                         const SkBitmap& bitmap) {
+void ArcWallpaperHandler::OnImageDecoded(const SkBitmap& bitmap) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  inflight_requests_.erase(base::WrapUnique(request));
   SetBitmapAsWallpaper(bitmap);
 }
 
-void ArcWallpaperHandler::OnDecodeImageFailed(ImageRequestImpl* request) {
+void ArcWallpaperHandler::OnDecodeImageFailed() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  inflight_requests_.erase(base::WrapUnique(request));
   LOG(ERROR) << "Failed to decode wallpaper image.";
 }
 
 }  // namespace arc