Adds a WebPageScheduler and a WebFrameScheduler

public/platform/WebScheduler.h

Index: public/platform/WebScheduler.h
diff --git a/public/platform/WebScheduler.h b/public/platform/WebScheduler.h
index 56baaa9c001c4a426fed74f1eeab809c68415fb3..dd0105f813b4eac613438a7fe0e00f440197ed86 100644
--- a/public/platform/WebScheduler.h
+++ b/public/platform/WebScheduler.h
@@ -11,6 +11,7 @@
 
 namespace blink {
 
+class WebPageScheduler;
 class WebTraceLocation;
 
 // This class is used to submit tasks and pass other information from Blink to
@@ -72,6 +73,9 @@ public:
     // Returns a WebTaskRunner for timer tasks. Can be called from any thread.
     virtual WebTaskRunner* timerTaskRunner() { return nullptr; }
 
+    // Creates a new WebPageScheduler. Must be called from the associated WebThread.
+    virtual WebPageScheduler* createPageScheduler() { return nullptr; }
+
     // Suspends the timer queue and increments the timer queue suspension count.
     // May only be called from the main thread.
     virtual void suspendTimerQueue() { }