Implement idle task scheduling.

Source/wtf/DoubleBufferedDeque.h

Index: Source/wtf/DoubleBufferedDeque.h
diff --git a/Source/wtf/DoubleBufferedDeque.h b/Source/wtf/DoubleBufferedDeque.h
index 5343f00c7770b37326eabc4f8e00fe1eb0ced0a7..eacfabf11b017b82424c6e0151e18af79dc53592 100644
--- a/Source/wtf/DoubleBufferedDeque.h
+++ b/Source/wtf/DoubleBufferedDeque.h
@@ -14,10 +14,11 @@ namespace WTF {
 template <typename T> class DoubleBufferedDeque {
     WTF_MAKE_NONCOPYABLE(DoubleBufferedDeque);
 public:
+    typedef typename PassTraits<T>::PassType PassType;
     DoubleBufferedDeque()
         : m_activeIndex(0) { }
 
-    void append(const T& value)
+    void append(const PassType& value)

[Sami, 2014/09/24 14:00:40]

Is this an optimization to avoid copies or something else?

[rmcilroy, 2014/09/29 17:42:58]

This is required to be able to create a DoubleBufferedDeque with OwnPtr or
RefPtr because the append function needs to use the pass type (PassOwnPtr)
rather than an OwnPtr (which wouldn't compile).  It shouldn't make any
difference on templated types which are not OwnPtr or RefPtr (PassType == T in
those cases).

     {
         m_queue[m_activeIndex].append(value);
     }