[Task Migration][Extensions] Update echoPrivate

Update the echoPrivate API to use the new task scheduling API, as well
as the dedicated Extensions-related file task runner.

Bug: 689520
Bug: 750122
Change-Id: Ie6d403cb700c71bc9faabd828b2f40f0826f85bd
Reviewed-on: https://chromium-review.googlesource.com/598464
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491515}

chrome/browser/chromeos/extensions/echo_private_api.cc

@@ -12,6 +12,7 @@
 #include "base/location.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
@@ -25,14 +26,12 @@
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/prefs/scoped_user_pref_update.h"
-#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
+#include "extensions/browser/extension_file_task_runner.h"
 #include "extensions/common/extension.h"
 
 namespace echo_api = extensions::api::echo_private;
 
-using content::BrowserThread;
-
 namespace {
 
 // URL of "More info" link shown in echo dialog in GetUserConsent function.
@@ -141,13 +140,12 @@ EchoPrivateGetOobeTimestampFunction::~EchoPrivateGetOobeTimestampFunction() {
 }
 
 bool EchoPrivateGetOobeTimestampFunction::RunAsync() {
-  BrowserThread::PostTaskAndReplyWithResult(
-      BrowserThread::FILE, FROM_HERE,
+  base::PostTaskAndReplyWithResult(
+      extensions::GetExtensionFileTaskRunner().get(), FROM_HERE,
       base::Bind(
-          &EchoPrivateGetOobeTimestampFunction::GetOobeTimestampOnFileThread,
+          &EchoPrivateGetOobeTimestampFunction::GetOobeTimestampOnFileSequence,
           this),
-      base::Bind(
-          &EchoPrivateGetOobeTimestampFunction::SendResponse, this));
+      base::Bind(&EchoPrivateGetOobeTimestampFunction::SendResponse, this));
   return true;
 }
 
@@ -155,8 +153,9 @@ bool EchoPrivateGetOobeTimestampFunction::RunAsync() {
 // The timestamp is used to determine when the user first activates the device.
 // If we can get the timestamp info, return it as yyyy-mm-dd, otherwise, return
 // an empty string.
-bool EchoPrivateGetOobeTimestampFunction::GetOobeTimestampOnFileThread() {
-  DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+bool EchoPrivateGetOobeTimestampFunction::GetOobeTimestampOnFileSequence() {
+  DCHECK(
+      extensions::GetExtensionFileTaskRunner()->RunsTasksInCurrentSequence());
 
   const char kOobeTimestampFile[] = "/home/chronos/.oobe_completed";
   std::string timestamp = "";

chrome/browser/chromeos/extensions/echo_private_api.h

@@ -49,7 +49,7 @@ class EchoPrivateGetOobeTimestampFunction
   bool RunAsync() override;
 
  private:
-  bool GetOobeTimestampOnFileThread();
+  bool GetOobeTimestampOnFileSequence();
   DECLARE_EXTENSION_FUNCTION("echoPrivate.getOobeTimestamp",
                              ECHOPRIVATE_GETOOBETIMESTAMP)
 };