Fix all dartanalyzer errors in dart:sky except the Native ones.

Fix all dartanalyzer errors in dart:sky except the Native ones.

I also fixed all warnings. :)

This is the only error remaining:
[error] Native functions can only be declared in the SDK and code
that is loaded through native extensions

My understanding is that we need to do something similar to:
https://codereview.chromium.org/950063002/
in order to work around the 'native' issue.

R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/14270f1151aacfa650985c4333572c356d15c024

[abarth-chromium, 2015-03-05 20:42:37]

lgtm

[eseidel, 2015-03-05 21:36:52]

Committed patchset #1 (id:1) manually as
14270f1151aacfa650985c4333572c356d15c024 (presubmit successful).

[jamesr, 2015-03-05 22:21:08]

jamesr@chromium.org changed reviewers:
+ jamesr@chromium.org

[jamesr, 2015-03-05 22:21:08]

Teh sky tests are all red on the bots:

Regressions: Unexpected timeouts (1)
  events/custom-event.sky [ Timeout ]

and I see no tryruns :(

[tonyg, 2015-03-05 23:04:23]

tonyg@chromium.org changed reviewers:
+ jimbe@chromium.org

[tonyg, 2015-03-05 23:05:01]

On 2015/03/05 22:21:08, jamesr wrote:
> Teh sky tests are all red on the bots:
> 
> Regressions: Unexpected timeouts (1)
>   events/custom-event.sky [ Timeout ]
> 
> and I see no tryruns :(

[+jimbe] whose roll is help up on this