Add an option to trace the debug protocol to the dart binary:

Add an option to trace the debug protocol to the dart binary:

  --trace_debug_protocol

------------------------
Sample output:

[>>>] Sending message to debug fd 10:
{ "event": "isolate", "params": { "reason": "created", "id": 7114 }}
[>>>] Sending message to debug fd 10:
{ "event": "paused", "params": { "reason": "breakpoint", "isolateId": 7114,"location": { "url":"file:\/\/\/Users\/turnidge\/dart\/DebuggingExample\/bin\/debuggingexample.dart","libraryId":14,"tokenOffset":193}}}
[<<<] Receiving message from debug fd 10:
{"id":1,"command":"getStackTrace","params":{"isolateId":7114}}
[>>>] Sending message to debug fd 10:
{ "id": 1, "result": {"callFrames" : [ {"functionName":"main","location": { "url":"file:\/\/\/Users\/turnidge\/dart\/DebuggingExample\/bin\/debuggingexample.dart","libraryId":14,"tokenOffset":193},"locals":[]}]}}

Committed: https://code.google.com/p/dart/source/detail?r=29477

[turnidge, 2013-10-21 20:13:55]

Small change to help me study the debug protocol.

[hausner, 2013-10-21 20:23:03]

I'm not sure this works with other embedders, e.g. Dartium, since there is no
definition of the the flag in that case.

Maybe use the same mechanism as for the verbose_debug flag?

[turnidge, 2013-10-29 18:52:56]

On 2013/10/21 20:23:03, hausner wrote:
> I'm not sure this works with other embedders, e.g. Dartium, since there is no
> definition of the the flag in that case.
> 
> Maybe use the same mechanism as for the verbose_debug flag?

As discussed offline, should not affect other embedders -- all code is in bin
directory which only affects standalone vm.

Submitting TBR, as all changes are under a flag and I need it for some other
work.  Please let me know if you have any edits and I will apply them.

[turnidge, 2013-10-29 18:53:19]

Committed patchset #3 manually as r29477 (presubmit successful).