Backport some tests in /chrome/browser/ssl to SingleThreadTaskEnvironment

These tests were previously migrated from single-threaded MessageLoop to
a multi-threaded TaskEnvironment (then named ScopedTaskEnvironment) as
part of crbug.com/891670.

//base OWNERS decided in retrospect that it was better to keep a
single-threaded option for TaskEnvironment and introduced
SingleThreadTaskEnvironment. This CL retrofits that decision for
/chrome/browser/ssl.

This CL is a no-op if it passes CQ.

This CL was uploaded by git cl split.

R=rsleevi@chromium.org

Bug: 891670
Change-Id: I827b531ccd4b0344dbb14656c506c413c09374ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1786905
Auto-Submit: Gabriel Charette <gab@chromium.org>
Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Commit-Queue: Ryan Sleevi <rsleevi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693949}

chrome/browser/ssl/certificate_error_reporter_unittest.cc

@@ -49,8 +49,8 @@ class ErrorReporterTest : public ::testing::Test {
   ~ErrorReporterTest() override {}
 
  protected:
-  base::test::TaskEnvironment task_environment_{
-      base::test::TaskEnvironment::MainThreadType::IO};
+  base::test::SingleThreadTaskEnvironment task_environment_{
+      base::test::SingleThreadTaskEnvironment::MainThreadType::IO};
   uint8_t server_public_key_[32];
   uint8_t server_private_key_[32];
 

chrome/browser/ssl/ssl_config_service_manager_pref_unittest.cc

@@ -84,7 +84,7 @@ class SSLConfigServiceManagerPrefTest : public testing::Test,
   }
 
  protected:
-  base::test::TaskEnvironment task_environment_;
+  base::test::SingleThreadTaskEnvironment task_environment_;
 
   TestingPrefServiceSimple local_state_;