Eliminate base::PostTask legacy call in recovery_component_installer.cc

Bug: 1026641
Change-Id: I14eaebf153dd419c4453cb22b9c5fb8be7f5add5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2229242Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Commit-Queue: Sorin Jianu <sorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774912}

chrome/browser/component_updater/recovery_component_installer.cc

@@ -416,7 +416,8 @@ void RecoveryComponentInstaller::Install(
   auto result = update_client::InstallFunctionWrapper(
       base::BindOnce(&RecoveryComponentInstaller::DoInstall,
                      base::Unretained(this), std::cref(unpack_path)));
-  base::PostTask(FROM_HERE, base::BindOnce(std::move(callback), result));
+  content::GetUIThreadTaskRunner({})->PostTask(
+      FROM_HERE, base::BindOnce(std::move(callback), result));
 }
 
 bool RecoveryComponentInstaller::DoInstall(