Switch BookmarkFaviconFetcher to the TaskScheduler API.

chrome/browser/bookmarks/bookmark_html_writer.cc

Index: chrome/browser/bookmarks/bookmark_html_writer.cc
diff --git a/chrome/browser/bookmarks/bookmark_html_writer.cc b/chrome/browser/bookmarks/bookmark_html_writer.cc
index 2ebc2621949aa5cae8166b75084bacc2d51b5bc1..48690b77d83499664857ecfeba688d4c3cc6d5c3 100644
--- a/chrome/browser/bookmarks/bookmark_html_writer.cc
+++ b/chrome/browser/bookmarks/bookmark_html_writer.cc
@@ -14,6 +14,7 @@
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/files/file.h"
+#include "base/lazy_instance.h"

[gab, 2017/07/20 19:11:14]

unused

[Sébastien Marchand, 2017/07/21 15:45:25]

Done.

 #include "base/location.h"
 #include "base/macros.h"
 #include "base/single_thread_task_runner.h"
@@ -448,8 +449,9 @@ void BookmarkFaviconFetcher::ExecuteWriter() {
   // for the duration of the write), as such we make a copy of the
   // BookmarkModel using BookmarkCodec then write from that.
   BookmarkCodec codec;
-  BrowserThread::PostTask(
-      BrowserThread::FILE, FROM_HERE,
+
+  background_io_task_runner_->PostTask(
+      FROM_HERE,
       base::BindOnce(
           &Writer::DoWrite,
           new Writer(codec.Encode(