Change GotDataCallback to scoped_refptr<base::RefCountedMemory>

BUG=571198

Review URL: https://codereview.chromium.org/1536173002

Cr-Commit-Position: refs/heads/master@{#368097}
diff --git a/base/memory/ref_counted_memory.h b/base/memory/ref_counted_memory.h
index 0372c87..f37a860 100644
--- a/base/memory/ref_counted_memory.h
+++ b/base/memory/ref_counted_memory.h
@@ -107,7 +107,7 @@
   // Constructs a RefCountedString object by performing a swap. (To non
   // destructively build a RefCountedString, use the default constructor and
   // copy into object->data()).
-  static RefCountedString* TakeString(std::string* to_destroy);
+  static scoped_refptr<RefCountedString> TakeString(std::string* to_destroy);
 
   // Overridden from RefCountedMemory:
   const unsigned char* front() const override;