TParseContext::addConstVectorNode() was returning a
TIntermTyped* variable of the wrong type if a swizzle
was of a different size than the vector's size. When
parseVectorFields() fails, fields.num is reset to 1,
which no longer matches fieldString.size(), so
fieldString.size() should not have been used. To
avoid future errors, the proper type is now set
directly within TParseContext::addConstVectorNode().

Bug chromium:796776

Change-Id: Id5e8d1b94d0a03fcf5ef6f5deeb77581bc070288
Reviewed-on: https://swiftshader-review.googlesource.com/17089Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>