Support JSON-RPC 2.0-compatible VM service events.

Support JSON-RPC 2.0-compatible VM service events.

This adds a parameter to streamListen that will cause it to produce JSON-RPC
2.0-compatible events.

R=turnidge@google.com

Committed: https://github.com/dart-lang/sdk/commit/61ea0618ce6e29cf101bc9c062222f04b97f211a

[nweiz, 2015-07-27 23:36:54]

nweiz@google.com changed reviewers:
+ johnmccutchan@google.com

[nweiz, 2015-07-27 23:36:55]

Note that this follows my original proposal for the JSON-RPC event format; it
may need to be updated later to address
https://github.com/dart-lang/sdk/issues/23897#issuecomment-125367996.

[turnidge, 2015-07-27 23:45:39]

turnidge@google.com changed reviewers:
+ turnidge@google.com

[Cutch, 2015-07-27 23:48:12]

On 2015/07/27 23:36:55, nweiz wrote:
> Note that this follows my original proposal for the JSON-RPC event format; it
> may need to be updated later to address
> https://github.com/dart-lang/sdk/issues/23897#issuecomment-125367996.

I'm going to leave this to Todd but I wonder if we can get away without offering
backwards compatibility (because we have so few external [near zero] clients to
the service).

[nweiz, 2015-07-28 00:24:16]

PTAL

I removed backwards incompatibility and changed to Todd's notification format.

[turnidge, 2015-07-28 21:20:43]

lgtm

Thank you for this and your other work on the protocol.  Much appreciated.

[nweiz, 2015-07-29 00:17:44]

Committed patchset #2 (id:20001) manually as
61ea0618ce6e29cf101bc9c062222f04b97f211a (presubmit successful).