Replace usage of std::exception by std::runtime_error

BUG=angleproject:892

Change-Id: I214fe6a93944dcfb39b0633f46caf3b1187bd5d3
Reviewed-on: https://chromium-review.googlesource.com/275815Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>