Resume a backgrounded renderer that was purged and suspended

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

Index: third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
index 5a17f616dcb971ae9f4446b8c1cd466aa65370f2..057da7f02acfb54fa07cba29e24a543ace6754a7 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
@@ -481,7 +481,7 @@ void RendererSchedulerImpl::OnRendererForegrounded() {
   MainThreadOnly().background_main_thread_load_tracker.Pause(now);
 
   suspend_timers_when_backgrounded_closure_.Cancel();
-  ResumeTimerQueueWhenForegrounded();
+  ResumeTimerQueueWhenForegroundedOrResumed();
 }
 
 void RendererSchedulerImpl::SuspendRenderer() {
@@ -500,6 +500,16 @@ void RendererSchedulerImpl::SuspendRenderer() {
   SuspendTimerQueueWhenBackgrounded();
 }
 
+void RendererSchedulerImpl::ResumeRenderer() {
+  helper_.CheckOnValidThread();
+  DCHECK(MainThreadOnly().renderer_backgrounded);
+  if (helper_.IsShutdown())
+    return;
+  suspend_timers_when_backgrounded_closure_.Cancel();
+  MainThreadOnly().renderer_suspended = false;
+  ResumeTimerQueueWhenForegroundedOrResumed();
+}
+
 void RendererSchedulerImpl::EndIdlePeriod() {
   if (MainThreadOnly().in_idle_period_for_testing)
     return;
@@ -1376,8 +1386,10 @@ void RendererSchedulerImpl::SuspendTimerQueueWhenBackgrounded() {
   ForceUpdatePolicy();
 }
 
-void RendererSchedulerImpl::ResumeTimerQueueWhenForegrounded() {
-  DCHECK(!MainThreadOnly().renderer_backgrounded);
+void RendererSchedulerImpl::ResumeTimerQueueWhenForegroundedOrResumed() {
+  DCHECK(!MainThreadOnly().renderer_backgrounded ||
+         (MainThreadOnly().renderer_backgrounded &&
+          !MainThreadOnly().renderer_suspended));
   if (!MainThreadOnly().timer_queue_suspended_when_backgrounded)
     return;