mojo: Fix Blink's shutdown sequence in AxProviderImplTest

components/scheduler/renderer/renderer_scheduler_impl.cc

Index: components/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/components/scheduler/renderer/renderer_scheduler_impl.cc b/components/scheduler/renderer/renderer_scheduler_impl.cc
index 48c4c1b2228d3de8dd51845e05841d517f37a517..7827a2c3cfa2f805484dc14dae07781fe58c8007 100644
--- a/components/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/components/scheduler/renderer/renderer_scheduler_impl.cc
@@ -38,6 +38,7 @@ RendererSchedulerImpl::RendererSchedulerImpl(
           helper_.ControlTaskRunner()),
       current_policy_(Policy::NORMAL),
       renderer_hidden_(false),
+      was_shutdown_(false),
       last_input_type_(blink::WebInputEvent::Undefined),
       input_stream_state_(InputStreamState::INACTIVE),
       policy_may_need_update_(&incoming_signals_lock_),
@@ -61,10 +62,15 @@ RendererSchedulerImpl::~RendererSchedulerImpl() {
   TRACE_EVENT_OBJECT_DELETED_WITH_ID(
       TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "RendererScheduler",
       this);
+  // Ensure the renderer scheduler was shut down explicitly, because otherwise
+  // we could end up having stale pointers to the Blink heap which has been
+  // terminated by this point.
+  DCHECK(was_shutdown_);
 }
 
 void RendererSchedulerImpl::Shutdown() {
   helper_.Shutdown();
+  was_shutdown_ = true;
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>