Add a virtual destructor to WebCredentialManagerClient.

third_party/WebKit/public/platform/WebCredentialManagerClient.h

Index: third_party/WebKit/public/platform/WebCredentialManagerClient.h
diff --git a/third_party/WebKit/public/platform/WebCredentialManagerClient.h b/third_party/WebKit/public/platform/WebCredentialManagerClient.h
index fa0a63f94b9f63b406455d63173771546337a540..044599f4741cb64e6eefaa50fcf7f0941e057b9c 100644
--- a/third_party/WebKit/public/platform/WebCredentialManagerClient.h
+++ b/third_party/WebKit/public/platform/WebCredentialManagerClient.h
@@ -36,6 +36,9 @@ class WebCredentialManagerClient {
                            bool include_passwords,
                            const WebVector<WebURL>& federations,
                            RequestCallbacks*) {}
+
+ protected:
+  virtual ~WebCredentialManagerClient() {}
 };
 
 }  // namespace blink