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..c914eba7fb06acf6e09e1553dbb7838349f3d59b 100644
--- a/Source/platform/scheduler/Scheduler.cpp
+++ b/Source/platform/scheduler/Scheduler.cpp
@@ -13,13 +13,13 @@
 namespace blink {
 
 class IdleTaskRunner : public WebScheduler::IdleTask {
+    WTF_MAKE_NONCOPYABLE(IdleTaskRunner);
 public:
-    explicit IdleTaskRunner(PassOwnPtr<Scheduler::IdleTask> task)
-        : m_task(task)
+    explicit IdleTaskRunner(PassOwnPtr<Scheduler::IdleTask> task) : m_task(task)
     {
     }
 
-    virtual ~IdleTaskRunner()
+    ~IdleTaskRunner() override
     {
     }
 
@@ -32,6 +32,26 @@ private:
     OwnPtr<Scheduler::IdleTask> m_task;
 };
 
+class ClosureRunner : public WebThread::Task {
+    WTF_MAKE_NONCOPYABLE(ClosureRunner);
+public:
+    explicit ClosureRunner(PassOwnPtr<Closure> closure) : m_closure(closure)
+    {
+    }
+
+    ~ClosureRunner() override
+    {
+    }
+
+    // WebThread::Task implementation.
+    void run() override
+    {
+        (*m_closure)();
+    }
+private:
+    OwnPtr<Closure> m_closure;
+};
+
 Scheduler* Scheduler::s_sharedScheduler = nullptr;
 
 void Scheduler::shutdown()
@@ -64,6 +84,18 @@ void Scheduler::postIdleTask(const TraceLocation& location, PassOwnPtr<IdleTask>
         m_webScheduler->postIdleTask(WebTraceLocation(location), new IdleTaskRunner(idleTask));
 }
 
+void Scheduler::postLoadingTask(const TraceLocation& location, PassOwnPtr<Closure> closure)
+{
+    if (m_webScheduler)
+        m_webScheduler->postLoadingTask(WebTraceLocation(location), new ClosureRunner(closure));
+}
+
+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)