Move crossThreadBind() from platform/ to wtf/

third_party/WebKit/Source/wtf/Functional.h

Index: third_party/WebKit/Source/wtf/Functional.h
diff --git a/third_party/WebKit/Source/wtf/Functional.h b/third_party/WebKit/Source/wtf/Functional.h
index 34f721557c687bf5fb58009f24ec7e367afb56dc..bdcff7c12602e8cfd6f35a9fb937b235663cc1e4 100644
--- a/third_party/WebKit/Source/wtf/Functional.h
+++ b/third_party/WebKit/Source/wtf/Functional.h
@@ -61,8 +61,19 @@ namespace WTF {
 // WTF::bind() and WTF::Closure should be used for same-thread closures
 // only, i.e. the closures must be created, executed and destructed on
 // the same thread.
-// Use crossThreadBind() and CrossThreadClosure if the function/task is called
-// or destructed on a (potentially) different thread from the current thread.
+//
+// Use WTF::crossThreadBind() and WTF::CrossThreadClosure if the function/task
+// is called or destructed on a (potentially) different thread from the current
+// thread.
+// WTF::crossThreadBind() applies CrossThreadCopier to the arguments.
+// Example:
+//     void func1(int, const String&);
+//     f = crossThreadBind(func1, 42, str);
+// func1(42, str2) will be called when |f()| is executed,
+// where |str2| is a deep copy of |str| (created by str.isolatedCopy()).
+// Don't (if you pass the task across threads):
+//     bind(func1, 42, str);
+//     bind(func1, 42, str.isolatedCopy());
 
 // WTF::bind() and move semantics
 // ==============================
@@ -269,11 +280,19 @@ std::unique_ptr<Function<base::MakeUnboundRunType<FunctionType, BoundParameters.
     return bindInternal<SameThreadAffinity>(function, std::forward<BoundParameters>(boundParameters)...);
 }
 
+template <typename FunctionType, typename... BoundParameters>
+std::unique_ptr<Function<base::MakeUnboundRunType<FunctionType, BoundParameters...>, CrossThreadAffinity>> crossThreadBind(FunctionType function, BoundParameters&&... boundParameters)
+{
+    return bindInternal<CrossThreadAffinity>(function, CrossThreadCopier<typename std::decay<BoundParameters>::type>::copy(std::forward<BoundParameters>(boundParameters))...);
+}
+
 typedef Function<void(), SameThreadAffinity> Closure;
 typedef Function<void(), CrossThreadAffinity> CrossThreadClosure;
 
 } // namespace WTF
 
+using WTF::crossThreadBind;
+
 using WTF::passed;
 using WTF::unretained;
 using WTF::crossThreadUnretained;