Add a virtual destructor to WebCredentialManagerClient.

content/shell/test_runner/mock_credential_manager_client.h

Index: content/shell/test_runner/mock_credential_manager_client.h
diff --git a/content/shell/test_runner/mock_credential_manager_client.h b/content/shell/test_runner/mock_credential_manager_client.h
index a41626bdd56853e051e366d41c9df4d5020eacaa..28f2adf4e9560bc45f38bf2e8c0ab3656cf28f07 100644
--- a/content/shell/test_runner/mock_credential_manager_client.h
+++ b/content/shell/test_runner/mock_credential_manager_client.h
@@ -22,7 +22,7 @@ namespace test_runner {
 class MockCredentialManagerClient : public blink::WebCredentialManagerClient {
  public:
   MockCredentialManagerClient();
-  virtual ~MockCredentialManagerClient();
+  ~MockCredentialManagerClient() override;
 
   // We take ownership of the |credential|.
   void SetResponse(blink::WebCredential* credential);