Revert of Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc.

extensions/browser/content_hash_fetcher.cc

Index: extensions/browser/content_hash_fetcher.cc
diff --git a/extensions/browser/content_hash_fetcher.cc b/extensions/browser/content_hash_fetcher.cc
index 1f73cb626c7454f4e82661f58cb9ce8b329f846d..7962630b26352f41dc0df07a19e442ea68a71d58 100644
--- a/extensions/browser/content_hash_fetcher.cc
+++ b/extensions/browser/content_hash_fetcher.cc
@@ -18,7 +18,8 @@
 #include "base/memory/ref_counted.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/synchronization/lock.h"
-#include "base/task_scheduler/post_task.h"
+#include "base/task_runner_util.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/timer/elapsed_timer.h"
 #include "base/version.h"
 #include "content/public/browser/browser_thread.h"
@@ -195,10 +196,11 @@
 void ContentHashFetcherJob::Start() {
   base::FilePath verified_contents_path =
       file_util::GetVerifiedContentsPath(extension_path_);
-  base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, base::TaskTraits().MayBlock().WithPriority(
-                     base::TaskPriority::USER_VISIBLE),
-      base::Bind(&ContentHashFetcherJob::LoadVerifiedContents, this,
+  base::PostTaskAndReplyWithResult(
+      content::BrowserThread::GetBlockingPool(),
+      FROM_HERE,
+      base::Bind(&ContentHashFetcherJob::LoadVerifiedContents,
+                 this,
                  verified_contents_path),
       base::Bind(&ContentHashFetcherJob::DoneCheckingForVerifiedContents,
                  this));
@@ -287,12 +289,12 @@
     base::FilePath destination =
         file_util::GetVerifiedContentsPath(extension_path_);
     size_t size = response->size();
-    base::PostTaskWithTraitsAndReplyWithResult(
-        FROM_HERE, base::TaskTraits().MayBlock().WithPriority(
-                       base::TaskPriority::USER_VISIBLE),
+    base::PostTaskAndReplyWithResult(
+        content::BrowserThread::GetBlockingPool(),
+        FROM_HERE,
         base::Bind(&WriteFileHelper, destination, base::Passed(&response)),
-        base::Bind(&ContentHashFetcherJob::OnVerifiedContentsWritten, this,
-                   size));
+        base::Bind(
+            &ContentHashFetcherJob::OnVerifiedContentsWritten, this, size));
   } else {
     DoneFetchingVerifiedContents(false);
   }