base::RefCounted now DCHECKs when referenced from multiple threads.

storage/browser/blob/shareable_file_reference.h

Index: storage/browser/blob/shareable_file_reference.h
diff --git a/storage/browser/blob/shareable_file_reference.h b/storage/browser/blob/shareable_file_reference.h
index e2739dcf8604654772991a11d14239c1c20cba23..2e0cad014b0655ddaf119fa2fc4c5000e3caa23d 100644
--- a/storage/browser/blob/shareable_file_reference.h
+++ b/storage/browser/blob/shareable_file_reference.h
@@ -16,8 +16,9 @@ namespace storage {
 // same path if it already exists in its internal map.
 // This class is non-thread-safe and all methods must be called on a single
 // thread.
+// TODO(mgiuca): Avoid using UnsafeRefCounted. http://crbug.com/469952.
 class STORAGE_EXPORT ShareableFileReference
-    : public base::RefCounted<ShareableFileReference> {
+    : public base::UnsafeRefCounted<ShareableFileReference> {
  public:
   typedef ScopedFile::ScopeOutCallback FinalReleaseCallback;
 
@@ -60,7 +61,7 @@ class STORAGE_EXPORT ShareableFileReference
   void AddFinalReleaseCallback(const FinalReleaseCallback& callback);
 
  private:
-  friend class base::RefCounted<ShareableFileReference>;
+  friend class base::UnsafeRefCounted<ShareableFileReference>;
 
   ShareableFileReference(ScopedFile scoped_file);
   ~ShareableFileReference();