Move IdleTask to WebThread side 1/3

Source/platform/scheduler/Scheduler.cpp

Index: Source/platform/scheduler/Scheduler.cpp
diff --git a/Source/platform/scheduler/Scheduler.cpp b/Source/platform/scheduler/Scheduler.cpp
index e8744a6d67f5493a86444c207738309dadfe8b26..bdd1f196543842399f5a2bd26cfc5b5fa07cbae2 100644
--- a/Source/platform/scheduler/Scheduler.cpp
+++ b/Source/platform/scheduler/Scheduler.cpp
@@ -11,7 +11,7 @@
 
 namespace blink {
 
-class IdleTaskRunner : public WebScheduler::IdleTask {
+class IdleTaskRunner : public WebThread::IdleTask {
     WTF_MAKE_NONCOPYABLE(IdleTaskRunner);
 
 public:
@@ -24,7 +24,7 @@ public:
     {
     }
 
-    // WebScheduler::IdleTask implementation.
+    // WebThread::IdleTask implementation.
     void run(double deadlineSeconds) override
     {
         (*m_task)(deadlineSeconds);