Add deprecated WebSocket constructor.

Add deprecated WebSocket constructor.

BUG=
R=sgjesse@google.com

Committed: https://code.google.com/p/dart/source/detail?r=35791

[Søren Gjesse, 2014-05-06 08:13:03]

https://codereview.chromium.org/268673018/diff/1/sdk/lib/io/websocket.dart
File sdk/lib/io/websocket.dart (right):

https://codereview.chromium.org/268673018/diff/1/sdk/lib/io/websocket.dart#ne...
sdk/lib/io/websocket.dart:137: ' `implements` instead of `extends`.')
Maybe change

'Consider using `implements` instead of `extends`.'

to something like

'Use `implements` instead of `extends` if implementing this interface.'

[Anders Johnsen, 2014-05-06 08:17:04]

PTAL

https://codereview.chromium.org/268673018/diff/1/sdk/lib/io/websocket.dart
File sdk/lib/io/websocket.dart (right):

https://codereview.chromium.org/268673018/diff/1/sdk/lib/io/websocket.dart#ne...
sdk/lib/io/websocket.dart:137: ' `implements` instead of `extends`.')
On 2014/05/06 08:13:04, Søren Gjesse wrote:
> Maybe change
> 
> 'Consider using `implements` instead of `extends`.'
> 
> to something like
> 
> 'Use `implements` instead of `extends` if implementing this interface.'

Done.

[Søren Gjesse, 2014-05-06 08:56:13]

lgtm

[Anders Johnsen, 2014-05-06 08:56:38]

Committed patchset #2 manually as r35791 (presubmit successful).