Adds a didReceiveInputEvent api to the blink scheduler

public/platform/WebSchedulerProxy.h

Index: public/platform/WebSchedulerProxy.h
diff --git a/public/platform/WebSchedulerProxy.h b/public/platform/WebSchedulerProxy.h
index f59ff991caf0d8e6e2a9fcb8f6e0cd6785a9632b..9c32d77f6788e2d21cf97b50625dde415e00bd7b 100644
--- a/public/platform/WebSchedulerProxy.h
+++ b/public/platform/WebSchedulerProxy.h
@@ -27,6 +27,9 @@ public:
     // ownership of |Task|. Can be called from any thread.
     BLINK_PLATFORM_EXPORT void postCompositorTask(const WebTraceLocation&, WebThread::Task*);
 
+    // Tells the scheduler that the system received an input event and it should go into low latency mode for a while.
+    BLINK_PLATFORM_EXPORT void didReceiveInputEvent();
+
 private:
     WebSchedulerProxy();