Adds a CancellableTaskFactory and exposes postLoadingTasks to Blink

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 535f114114da747340502f20efd830cbf81440d0..60e42d04443736ca6a4ae5ec49ce85ac1003036f 100644
--- a/Source/platform/scheduler/Scheduler.cpp
+++ b/Source/platform/scheduler/Scheduler.cpp
@@ -13,13 +13,15 @@
 namespace blink {
 
 class IdleTaskRunner : public WebScheduler::IdleTask {
+    WTF_MAKE_NONCOPYABLE(IdleTaskRunner);
+
 public:
     explicit IdleTaskRunner(PassOwnPtr<Scheduler::IdleTask> task)
         : m_task(task)
     {
     }
 
-    virtual ~IdleTaskRunner()
+    ~IdleTaskRunner() override
     {
     }
 
@@ -64,6 +66,12 @@ void Scheduler::postIdleTask(const TraceLocation& location, PassOwnPtr<IdleTask>
         m_webScheduler->postIdleTask(WebTraceLocation(location), new IdleTaskRunner(idleTask));
 }
 
+void Scheduler::postLoadingTask(const TraceLocation& location, WebThread::Task* task)
+{
+    if (m_webScheduler)
+        m_webScheduler->postLoadingTask(WebTraceLocation(location), task);
+}
+
 bool Scheduler::shouldYieldForHighPriorityWork() const
 {
     if (m_webScheduler)