Add WTF::WrapRefPtr

WTF::WrapRefPtr is similar to WTF::WrapPassRefPtr, that is needed to
remove PassRefPtr from Blink.

Bug: 494719
Change-Id: I60deaf782a6ac2d9b24001e8ff01b55429bda287
Reviewed-on: https://chromium-review.googlesource.com/666941Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502152}

third_party/WebKit/Source/platform/wtf/RefPtr.h

@@ -214,6 +214,11 @@ RefPtr<T> AdoptRef(T* p) {
   return RefPtr<T>(p, RefPtr<T>::kAdoptRef);
 }
 
+template <typename T>
+RefPtr<T> WrapRefPtr(T* ptr) {
+  return RefPtr<T>(ptr);
+}
+
 }  // namespace WTF
 
 using WTF::RefPtr;