Remove references of MessageLoopForIO in /chrome/browser/ssl

MessageLoopForIO will go away soon use ScopedTaskEnvironment instead.

ScopedTaskEnvironment will per default start a ThreadPool, which should
be fine in most of the cases. If you believe your test needs to make sure
that no ThreadPool runs let me know and I will update the patch.

BUG=891670
This CL was uploaded by git cl split.

R=carlosil@chromium.org

Change-Id: I8a40cda13a2956cddde98da24717da74081f8457
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1733609
Auto-Submit: Carlos Caballero <carlscab@google.com>
Reviewed-by: Carlos IL <carlosil@chromium.org>
Commit-Queue: Carlos IL <carlosil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683638}

chrome/browser/ssl/certificate_error_reporter_unittest.cc

@@ -13,10 +13,10 @@
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/macros.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/string_piece.h"
 #include "base/test/bind_test_util.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/encrypted_messages/encrypted_message.pb.h"
 #include "components/encrypted_messages/message_encrypter.h"
 #include "net/http/http_status_code.h"
@@ -49,7 +49,8 @@ class ErrorReporterTest : public ::testing::Test {
   ~ErrorReporterTest() override {}
 
  protected:
-  base::MessageLoopForIO loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_{
+      base::test::ScopedTaskEnvironment::MainThreadType::IO};
   uint8_t server_public_key_[32];
   uint8_t server_private_key_[32];