RefCounted types should not have public destructors, delegate cleanup

chrome/common/net/gaia/oauth2_mint_token_flow.h

Index: chrome/common/net/gaia/oauth2_mint_token_flow.h
diff --git a/chrome/common/net/gaia/oauth2_mint_token_flow.h b/chrome/common/net/gaia/oauth2_mint_token_flow.h
index e50c526fce324b6a4f65f6fe383aa14938285e23..058012d984ea778ba07553dd0edd7844ae1cdb78 100644
--- a/chrome/common/net/gaia/oauth2_mint_token_flow.h
+++ b/chrome/common/net/gaia/oauth2_mint_token_flow.h
@@ -88,11 +88,12 @@ class OAuth2MintTokenFlow : public OAuth2ApiCallFlow {
 
   class Delegate {
    public:
-    Delegate() {}
-    virtual ~Delegate() {}
     virtual void OnMintTokenSuccess(const std::string& access_token) {}
     virtual void OnIssueAdviceSuccess(const IssueAdviceInfo& issue_advice)  {}
     virtual void OnMintTokenFailure(const GoogleServiceAuthError& error) {}
+
+   protected:
+    virtual ~Delegate() {}
   };
 
   // An interceptor for tests.