Drop unused 'ExceptionState&' parameters from WebGLRenderingContext.

Many WebGLRenderingContext methods claim in the IDL file to
RaiseExceptions, but end up stubbing out the implementation with
'UNUSED_PARAM(es)'. This mechanical patch removes the 'ExceptionState&'
parameter from these methods, the IDL file, and the callsites.

Review URL: https://chromiumcodereview.appspot.com/22370003

git-svn-id: svn://svn.chromium.org/blink/trunk@155622 bbb929c8-8fbe-4397-9dbb-9b2b20218538