Fix a data race on the ref count of AddToHomescreenDataFetcher

chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc

 // Copyright 2015 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/android/webapps/add_to_homescreen_data_fetcher.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/location.h"
 #include "base/strings/string16.h"
+#include "base/task_runner_util.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/android/offline_pages/offline_page_utils.h"
 #include "chrome/browser/android/shortcut_helper.h"
 #include "chrome/browser/android/webapk/webapk_web_manifest_checker.h"
 #include "chrome/browser/favicon/favicon_service_factory.h"
 #include "chrome/browser/installable/installable_manager.h"
 #include "chrome/browser/manifest/manifest_icon_selector.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/render_messages.h"
@@ skipping 44 matching lines @@
 AddToHomescreenDataFetcher::AddToHomescreenDataFetcher(
     content::WebContents* web_contents,
     int ideal_icon_size_in_px,
     int minimum_icon_size_in_px,
     int ideal_splash_image_size_in_px,
     int minimum_splash_image_size_in_px,
     int badge_size_in_px,
     bool check_webapk_compatibility,
     Observer* observer)
     : WebContentsObserver(web_contents),
+      background_task_runner_(
+          content::BrowserThread::GetBlockingPool()
+              ->GetTaskRunnerWithShutdownBehavior(
+                  base::SequencedWorkerPool::SKIP_ON_SHUTDOWN)),
       weak_observer_(observer),
       shortcut_info_(GetShortcutUrl(web_contents->GetBrowserContext(),
                                     web_contents->GetLastCommittedURL())),
       data_timeout_timer_(false, false),
       ideal_icon_size_in_px_(ideal_icon_size_in_px),
       minimum_icon_size_in_px_(minimum_icon_size_in_px),
       ideal_splash_image_size_in_px_(ideal_splash_image_size_in_px),
       minimum_splash_image_size_in_px_(minimum_splash_image_size_in_px),
       badge_size_in_px_(badge_size_in_px),
       check_webapk_compatibility_(check_webapk_compatibility),
@@ skipping 192 matching lines @@
       shortcut_info_.url, icon_types, threshold_to_get_any_largest_icon,
       base::Bind(&AddToHomescreenDataFetcher::OnFaviconFetched, this),
       &favicon_task_tracker_);
 }
 
 void AddToHomescreenDataFetcher::OnFaviconFetched(
     const favicon_base::FaviconRawBitmapResult& bitmap_result) {
   if (!web_contents() || !weak_observer_ || is_icon_saved_)
     return;
 
-  content::BrowserThread::GetBlockingPool()->PostWorkerTaskWithShutdownBehavior(
-      FROM_HERE, base::Bind(&AddToHomescreenDataFetcher::
-                                CreateLauncherIconFromFaviconInBackground,
-                            this, bitmap_result),
-      base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
+  base::PostTaskAndReplyWithResult(
+      background_task_runner_.get(), FROM_HERE,
+      base::Bind(&AddToHomescreenDataFetcher::
+                     CreateLauncherIconFromFaviconInBackground,
+                 base::Unretained(this), bitmap_result),
+      base::Bind(&AddToHomescreenDataFetcher::NotifyObserver,
+                 base::RetainedRef(this)));
 }
 
-void AddToHomescreenDataFetcher::CreateLauncherIconFromFaviconInBackground(
+SkBitmap AddToHomescreenDataFetcher::CreateLauncherIconFromFaviconInBackground(
     const favicon_base::FaviconRawBitmapResult& bitmap_result) {
   DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
 
   SkBitmap raw_icon;
   if (bitmap_result.is_valid()) {
     gfx::PNGCodec::Decode(bitmap_result.bitmap_data->front(),
                           bitmap_result.bitmap_data->size(), &raw_icon);
   }
 
   shortcut_info_.best_primary_icon_url = bitmap_result.icon_url;
-  CreateLauncherIconInBackground(raw_icon);
+  return CreateLauncherIconInBackground(raw_icon);
 }
 
 void AddToHomescreenDataFetcher::CreateLauncherIcon(const SkBitmap& raw_icon) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  content::BrowserThread::GetBlockingPool()->PostWorkerTaskWithShutdownBehavior(
-      FROM_HERE,
+  base::PostTaskAndReplyWithResult(
+      background_task_runner_.get(), FROM_HERE,
       base::Bind(&AddToHomescreenDataFetcher::CreateLauncherIconInBackground,
-                 this, raw_icon),
-      base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
+                 base::Unretained(this), raw_icon),
+      base::Bind(&AddToHomescreenDataFetcher::NotifyObserver,
+                 base::RetainedRef(this)));
 }
 
-void AddToHomescreenDataFetcher::CreateLauncherIconInBackground(
+SkBitmap AddToHomescreenDataFetcher::CreateLauncherIconInBackground(
     const SkBitmap& raw_icon) {
   DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
 
   SkBitmap primary_icon;
   bool is_generated = false;
   if (weak_observer_) {
     primary_icon = weak_observer_->FinalizeLauncherIconInBackground(
         raw_icon, shortcut_info_.url, &is_generated);
   }
 
   if (is_generated)
     shortcut_info_.best_primary_icon_url = GURL();
 
-  content::BrowserThread::PostTask(
-      content::BrowserThread::UI, FROM_HERE,
-      base::Bind(&AddToHomescreenDataFetcher::NotifyObserver, this,
-                 primary_icon));
+  return primary_icon;
 }
 
 void AddToHomescreenDataFetcher::NotifyObserver(const SkBitmap& primary_icon) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   if (!web_contents() || !weak_observer_ || is_icon_saved_)
     return;
 
   is_icon_saved_ = true;
   primary_icon_ = primary_icon;
   is_ready_ = true;
   weak_observer_->OnDataAvailable(shortcut_info_, primary_icon_, badge_icon_);
 }