Remove ScriptState::current() from CryptoResultImpl

ScriptState::current() should be called only in the binding layer. This CL removes ScriptState::current() from CryptoResultImpl.

BUG=357144

Review URL: https://codereview.chromium.org/294203007

git-svn-id: svn://svn.chromium.org/blink/trunk@174754 bbb929c8-8fbe-4397-9dbb-9b2b20218538