[scheduler] Fix --disable-background-timer-throttling flag.

third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h

Index: third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
diff --git a/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h b/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
index 8257671cd61b951964ed8dd95ffb99a6cd353d33..4056a5e8c565f25e9d662cfc8317f03a0c504598 100644
--- a/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
+++ b/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
@@ -95,6 +95,15 @@ class PLATFORM_EXPORT WebScheduler {
   virtual void RemovePendingNavigation(
       scheduler::RendererScheduler::NavigatingFrameType) = 0;
 
+  // Test helpers.
+
+  // Return a reference to an underlying RendererScheduler object.
+  // Can be null if there is no underlying RendererScheduler
+  // (e.g. worker threads).
+  virtual scheduler::RendererScheduler* GetRendererSchedulerForTest() {
+    return nullptr;
+  }
+
 #ifdef INSIDE_BLINK
   // Helpers for posting bound functions as tasks.
   typedef Function<void(double deadline_seconds)> IdleTask;