Fix login visual hitch on chromebook

chrome/browser/chromeos/login/user_image_loader.cc

Index: chrome/browser/chromeos/login/user_image_loader.cc
diff --git a/chrome/browser/chromeos/login/user_image_loader.cc b/chrome/browser/chromeos/login/user_image_loader.cc
index 4ea3c1c75d4276fa2077befef4d08b45fc049148..084f9ef67c4095e0604a6cf9cfbf0020168f3061 100644
--- a/chrome/browser/chromeos/login/user_image_loader.cc
+++ b/chrome/browser/chromeos/login/user_image_loader.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright (c) 2013 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.
 
@@ -9,6 +9,7 @@
 #include "base/file_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
+#include "base/threading/worker_pool.h"
 #include "chrome/browser/chromeos/login/helper.h"
 #include "chrome/browser/chromeos/login/user_image.h"
 #include "content/public/browser/browser_thread.h"
@@ -21,6 +22,8 @@ using content::BrowserThread;
 
 namespace chromeos {
 
+typedef base::SequencedWorkerPool::SequenceToken SequenceToken;
+
 UserImageLoader::ImageInfo::ImageInfo(int size,
                                       const LoadedCallback& loaded_cb)
     : size(size),
@@ -44,51 +47,67 @@ void UserImageLoader::Start(const std::string& filepath,
   target_message_loop_ = MessageLoop::current();
 
   ImageInfo image_info(size, loaded_cb);
-  BrowserThread::PostTask(
-      BrowserThread::FILE, FROM_HERE,
-      base::Bind(&UserImageLoader::LoadImage, this, filepath, image_info));
+  base::SequencedWorkerPool* pool = BrowserThread::GetBlockingPool();
+  SequenceToken sequence_token = pool->GetSequenceToken();
+  scoped_refptr<base::SequencedTaskRunner> task_runner = pool->
+      GetSequencedTaskRunnerWithShutdownBehavior(sequence_token,
+          base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
+  task_runner->PostTask(
+      FROM_HERE,
+      base::Bind(&UserImageLoader::LoadImage, this, filepath, image_info,
+                 task_runner));
 }
 
-void UserImageLoader::LoadImage(const std::string& filepath,
-                                const ImageInfo& image_info) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+void UserImageLoader::LoadImage(
+    const std::string& filepath,
+    const ImageInfo& image_info,
+    scoped_refptr<base::SequencedTaskRunner> task_runner) {
+  DCHECK(task_runner->RunsTasksOnCurrentThread());
 
   std::string image_data;
   file_util::ReadFileToString(FilePath(filepath), &image_data);
 
   scoped_refptr<ImageDecoder> image_decoder =
       new ImageDecoder(this, image_data, image_codec_);
-  image_info_map_.insert(std::make_pair(image_decoder.get(), image_info));
-  image_decoder->Start();
+  {
+    base::AutoLock lock(lock_);
+    image_info_map_.insert(std::make_pair(image_decoder.get(), image_info));
+  }
+  image_decoder->Start(task_runner);
 }
 
 void UserImageLoader::OnImageDecoded(const ImageDecoder* decoder,
                                      const SkBitmap& decoded_image) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-
-  ImageInfoMap::iterator info_it = image_info_map_.find(decoder);
-  if (info_it == image_info_map_.end()) {
-    NOTREACHED();
-    return;
+  ImageInfoMap::iterator info_it;
+  scoped_ptr<ImageInfo> image_info;
+  {
+    base::AutoLock lock(lock_);
+    info_it = image_info_map_.find(decoder);
+    if (info_it == image_info_map_.end()) {
+      NOTREACHED();
+      return;
+    }
+    image_info.reset(
+        new ImageInfo(info_it->second.size, info_it->second.loaded_cb));
+    image_info_map_.erase(info_it);
   }
 
-  const ImageInfo& image_info = info_it->second;
   SkBitmap final_image = decoded_image;
 
-  if (image_info.size > 0) {
+  if (image_info->size > 0) {
     // Auto crop the image, taking the largest square in the center.
     int size = std::min(decoded_image.width(), decoded_image.height());
     int x = (decoded_image.width() - size) / 2;
     int y = (decoded_image.height() - size) / 2;
     SkBitmap cropped_image =
         SkBitmapOperations::CreateTiledBitmap(decoded_image, x, y, size, size);
-    if (size > image_info.size) {
+    if (size > image_info->size) {
       // Also downsize the image to save space and memory.
       final_image =
           skia::ImageOperations::Resize(cropped_image,
                                         skia::ImageOperations::RESIZE_LANCZOS3,
-                                        image_info.size,
-                                        image_info.size);
+                                        image_info->size,
+                                        image_info->size);
     } else {
       final_image = cropped_image;
     }
@@ -101,25 +120,27 @@ void UserImageLoader::OnImageDecoded(const ImageDecoder* decoder,
     user_image.MarkAsSafe();
   target_message_loop_->PostTask(
       FROM_HERE,
-      base::Bind(image_info.loaded_cb, user_image));
-
-  image_info_map_.erase(info_it);
+      base::Bind(image_info->loaded_cb, user_image));
 }
 
 void UserImageLoader::OnDecodeImageFailed(const ImageDecoder* decoder) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-
-  ImageInfoMap::iterator info_it = image_info_map_.find(decoder);
-  if (info_it == image_info_map_.end()) {
-    NOTREACHED();
-    return;
+  ImageInfoMap::iterator info_it;
+  scoped_ptr<ImageInfo> image_info;
+  {
+    base::AutoLock lock(lock_);
+    info_it = image_info_map_.find(decoder);
+    if (info_it == image_info_map_.end()) {
+      NOTREACHED();
+      return;
+    }
+    image_info.reset(
+        new ImageInfo(info_it->second.size, info_it->second.loaded_cb));
+    image_info_map_.erase(decoder);
   }
 
-  const ImageInfo& image_info = info_it->second;
   target_message_loop_->PostTask(
       FROM_HERE,
-      base::Bind(image_info.loaded_cb, UserImage()));
-  image_info_map_.erase(decoder);
+      base::Bind(image_info->loaded_cb, UserImage()));
 }
 
 }  // namespace chromeos