Fix integration tests in src/chrome and src/extensions so that we can turn on IO thread checks wi...

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

Index: chrome/browser/chromeos/file_manager/file_manager_browsertest.cc
diff --git a/chrome/browser/chromeos/file_manager/file_manager_browsertest.cc b/chrome/browser/chromeos/file_manager/file_manager_browsertest.cc
index 0e9d776454dba7b75b9ef9d8c3e684f482494b38..06ecc1d949ebdfc36e176e66bf128e1e341d574f 100644
--- a/chrome/browser/chromeos/file_manager/file_manager_browsertest.cc
+++ b/chrome/browser/chromeos/file_manager/file_manager_browsertest.cc
@@ -6,6 +6,7 @@
 
 #include "base/macros.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/threading/thread_restrictions.h"
 #include "chrome/browser/chromeos/drive/file_system_util.h"
 #include "chrome/browser/chromeos/file_manager/file_manager_browsertest_base.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
@@ -631,6 +632,7 @@ class MultiProfileFileManagerBrowserTest : public FileManagerBrowserTestBase {
 
   // Adds a new user for testing to the current session.
   void AddUser(const TestAccountInfo& info, bool log_in) {
+    base::ThreadRestrictions::ScopedAllowIO allow_io;
     const AccountId account_id(AccountId::FromUserEmail(info.email));
     if (log_in) {
       session_manager::SessionManager::Get()->CreateSession(account_id,