Fix buildbreak on Linux GCC Add virtual destructor to SignalReceiver. class angle::SignalReceiver has virtual functions and accessible non-virtual destructor. This generates a compile error. Change-Id: Iced2ee94ad9268ab5c1d00ab336ab2cc98385afc Reviewed-on: https://chromium-review.googlesource.com/351930 Reviewed-by: Sami Väisänen <svaisanen@nvidia.com> Commit-Queue: Sami Väisänen <svaisanen@nvidia.com>