Make an interface's virtual dtor protected rather than public.

net/proxy/proxy_resolver_v8.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_PROXY_PROXY_RESOLVER_V8_H_
 #define NET_PROXY_PROXY_RESOLVER_V8_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/base/net_export.h"
@@ skipping 27 matching lines @@
     enum ResolveDnsOperation {
       DNS_RESOLVE,
       DNS_RESOLVE_EX,
       MY_IP_ADDRESS,
       MY_IP_ADDRESS_EX,
       NUM_DNS_OPERATIONS,
     };
 
     JSBindings() {}
 
-    virtual ~JSBindings() {}
-
     // Handler for "dnsResolve()", "dnsResolveEx()", "myIpAddress()",
     // "myIpAddressEx()". Returns true on success and fills |*output| with the
     // result.
     virtual bool ResolveDns(const std::string& host,
                             ResolveDnsOperation op,
                             std::string* output) = 0;
 
     // Handler for "alert(message)"
     virtual void Alert(const string16& message) = 0;
 
     // Handler for when an error is encountered. |line_number| may be -1
     // if a line number is not applicable to this error.
     virtual void OnError(int line_number, const string16& error) = 0;
+
+   protected:
+    virtual ~JSBindings() {}
   };
 
   // Constructs a ProxyResolverV8.
   ProxyResolverV8();
 
   virtual ~ProxyResolverV8();
 
   JSBindings* js_bindings() const { return js_bindings_; }
   void set_js_bindings(JSBindings* js_bindings) { js_bindings_ = js_bindings; }
 
@@ skipping 20 matching lines @@
   scoped_ptr<Context> context_;
 
   JSBindings* js_bindings_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyResolverV8);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_RESOLVER_V8_H_