Limit stack-allocated uses of CancellableTaskFactory(PassOwnPtr<Closure>).

Source/platform/scheduler/CancellableTaskFactory.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CancellableTaskFactory_h
 #define CancellableTaskFactory_h
 
 #include "platform/PlatformExport.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/WebScheduler.h"
@@ skipping 30 matching lines @@
     {
         return adoptPtr(new CancellableTaskFactory(WTF::bind(method, AllowCrossThreadWeakPersistent<T>(thisObject))));
     }
 
     template<typename T>
     static PassOwnPtr<CancellableTaskFactory> create(T* thisObject, void (T::*method)(), typename WTF::EnableIf<!IsGarbageCollectedType<T>::value>::Type* = nullptr)
     {
         return adoptPtr(new CancellableTaskFactory(WTF::bind(method, thisObject)));
     }
 
-    // Only intended used by unit tests. Please use leak safe create() factory method, if possible.
-    explicit CancellableTaskFactory(PassOwnPtr<Closure> closure)
-        : m_closure(closure)
-        , m_weakPtrFactory(this)
-    {
-    }
-
     bool isPending() const
     {
         return m_weakPtrFactory.hasWeakPtrs();
     }
 
     void cancel();
 
     // Returns a task that can be disabled by calling cancel().  The user takes
     // ownership of the task.  Creating a new task cancels any previous ones.
     WebTaskRunner::Task* cancelAndCreate();
 
+protected:
+    // Only intended used by unit tests wanting to stack allocate and/or pass in a closure value.
+    // Please use the create() factory method elsewhere.
+    explicit CancellableTaskFactory(PassOwnPtr<Closure> closure)
+        : m_closure(closure)
+        , m_weakPtrFactory(this)
+    {
+    }
+
 private:
     class CancellableTask : public WebTaskRunner::Task {
         WTF_MAKE_NONCOPYABLE(CancellableTask);
 
     public:
         explicit CancellableTask(WeakPtr<CancellableTaskFactory> weakPtr)
             : m_weakPtr(weakPtr) {}
 
         ~CancellableTask() override {}
 
         void run() override;
 
     private:
         WeakPtr<CancellableTaskFactory> m_weakPtr;
     };
 
     OwnPtr<Closure> m_closure;
     WeakPtrFactory<CancellableTaskFactory> m_weakPtrFactory;
 };
 
 } // namespace blink
 
 #endif // CancellableTaskFactory_h