Unite processing of all simple commands in command-line debugger.

Unite processing of all simple commands in command-line debugger.


BUG=
TEST=

Committed: https://code.google.com/p/dart/source/detail?r=7910

[Bill Hesse, 2012-05-23 09:15:04]

I could also index the map literal directly with [command], but the line would
wrap.

I changed cmd to command because the editor gives warnings (they are in the spec
as warnings) when you shadow a local variable or parameter.  You could also just
use the same variable - the outer cmd (now command) is always dead at the point
that you use the inner cmd.

[hausner, 2012-05-23 15:08:15]

lgtm