Disallow posting tasks to SequencedWorkerPools by default.

content/public/test/browser_test_base.cc

Index: content/public/test/browser_test_base.cc
diff --git a/content/public/test/browser_test_base.cc b/content/public/test/browser_test_base.cc
index 0b510beb8b483eefcdec4d63d0ceac8e1fa3d53e..2333cceee12396f5938785a2917750cb748aeeef 100644
--- a/content/public/test/browser_test_base.cc
+++ b/content/public/test/browser_test_base.cc
@@ -17,6 +17,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/sys_info.h"
 #include "base/test/test_timeouts.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "build/build_config.h"
 #include "content/browser/renderer_host/render_process_host_impl.h"
 #include "content/browser/tracing/tracing_controller_impl.h"
@@ -165,6 +166,13 @@ BrowserTestBase::BrowserTestBase()
   base::i18n::AllowMultipleInitializeCallsForTesting();
 
   embedded_test_server_.reset(new net::EmbeddedTestServer);
+
+  // SequencedWorkerPool is enabled by default in tests (see
+  // base::TestSuite::Initialize). In browser tests, disable it and expect it
+  // to be re-enabled as part of BrowserMainLoop::PreCreateThreads().
+  // TODO(fdoray): Remove this once the SequencedWorkerPool to TaskScheduler
+  // redirection experiment concludes https://crbug.com/622400.
+  base::SequencedWorkerPool::DisableForProcessForTesting();
 }
 
 BrowserTestBase::~BrowserTestBase() {