Migrate AddToHomescreenDataFetcher to use TaskScheduler.

chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc

Index: chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc
diff --git a/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc b/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc
index 41f846b3dd459183c4c582764fe1ee6fedb68d9a..4e31565c909d2fabbdc0af12c90faf790e31dcd0 100644
--- a/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc
+++ b/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc
@@ -9,11 +9,7 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/metrics/user_metrics.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 "base/task_scheduler/post_task.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"
@@ -28,7 +24,6 @@
 #include "content/public/browser/manifest_icon_selector.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
-#include "content/public/browser/web_contents_observer.h"
 #include "content/public/common/manifest.h"
 #include "third_party/WebKit/public/platform/modules/screen_orientation/WebScreenOrientationLockType.h"
 #include "ui/gfx/codec/png_codec.h"
@@ -77,11 +72,7 @@ AddToHomescreenDataFetcher::AddToHomescreenDataFetcher(
     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)),
+    : content::WebContentsObserver(web_contents),
       weak_observer_(observer),
       shortcut_info_(GetShortcutUrl(web_contents->GetBrowserContext(),
                                     web_contents->GetLastCommittedURL())),
@@ -290,16 +281,23 @@ void AddToHomescreenDataFetcher::FetchFavicon() {
 
 void AddToHomescreenDataFetcher::OnFaviconFetched(
     const favicon_base::FaviconRawBitmapResult& bitmap_result) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
   if (!web_contents() || !weak_observer_ || is_icon_saved_)
     return;
 
-  base::PostTaskAndReplyWithResult(
-      background_task_runner_.get(), FROM_HERE,
-      base::Bind(&AddToHomescreenDataFetcher::
-                     CreateLauncherIconFromFaviconInBackground,
-                 base::Unretained(this), bitmap_result),
-      base::Bind(&AddToHomescreenDataFetcher::NotifyObserver,
-                 base::RetainedRef(this)));
+  // The user is waiting for the icon to be processed before they can proceed
+  // with add to homescreen. But if we shut down, there's no point starting the
+  // image processing. Use USER_VISIBLE with MayBlock and SKIP_ON_SHUTDOWN.
+  base::PostTaskWithTraitsAndReplyWithResult(
+      FROM_HERE,
+      {base::MayBlock(), base::TaskPriority::USER_VISIBLE,
+       base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN},
+      base::BindOnce(&AddToHomescreenDataFetcher::
+                         CreateLauncherIconFromFaviconInBackground,
+                     base::Unretained(this), bitmap_result),
+      base::BindOnce(&AddToHomescreenDataFetcher::NotifyObserver,
+                     base::RetainedRef(this)));
 }
 
 SkBitmap AddToHomescreenDataFetcher::CreateLauncherIconFromFaviconInBackground(
@@ -318,12 +316,19 @@ SkBitmap AddToHomescreenDataFetcher::CreateLauncherIconFromFaviconInBackground(
 
 void AddToHomescreenDataFetcher::CreateLauncherIcon(const SkBitmap& raw_icon) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  base::PostTaskAndReplyWithResult(
-      background_task_runner_.get(), FROM_HERE,
-      base::Bind(&AddToHomescreenDataFetcher::CreateLauncherIconInBackground,
-                 base::Unretained(this), raw_icon),
-      base::Bind(&AddToHomescreenDataFetcher::NotifyObserver,
-                 base::RetainedRef(this)));
+
+  // The user is waiting for the icon to be processed before they can proceed
+  // with add to homescreen. But if we shut down, there's no point starting the
+  // image processing. Use USER_VISIBLE with MayBlock and SKIP_ON_SHUTDOWN.
+  base::PostTaskWithTraitsAndReplyWithResult(
+      FROM_HERE,
+      {base::MayBlock(), base::TaskPriority::USER_VISIBLE,
+       base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN},
+      base::BindOnce(
+          &AddToHomescreenDataFetcher::CreateLauncherIconInBackground,
+          base::Unretained(this), raw_icon),
+      base::BindOnce(&AddToHomescreenDataFetcher::NotifyObserver,
+                     base::RetainedRef(this)));
 }
 
 SkBitmap AddToHomescreenDataFetcher::CreateLauncherIconInBackground(