small cleanups to dart_runtime.js

small cleanups to dart_runtime.js
these were caught by the webstorm ES6 plugin
biggest one is strict mode doesn't like local functions except at top level, I think becasue the name is not scoped correctly (for historical reasons). Instead `let name = () => ...;`  allows correct scoping for `name`.

R=vsm@google.com

Committed: https://github.com/dart-lang/dev_compiler/commit/1ed893095df96a2b090bbb574919c09c5a3f719d

[Jennifer Messerly, 2015-05-29 23:02:20]

jmesserly@google.com changed reviewers:
+ leafp@google.com, vsm@google.com

[Jennifer Messerly, 2015-05-29 23:02:21]

https://codereview.chromium.org/1152783005/diff/1/lib/runtime/dart_runtime.js
File lib/runtime/dart_runtime.js (left):

https://codereview.chromium.org/1152783005/diff/1/lib/runtime/dart_runtime.js...
lib/runtime/dart_runtime.js:29: function formalParameterList(fn) {
dead code

https://codereview.chromium.org/1152783005/diff/1/lib/runtime/dart_runtime.js...
lib/runtime/dart_runtime.js:1025: return sig;
it doesn't like unnecessary locals

[vsm, 2015-05-29 23:07:37]

lgtm

https://codereview.chromium.org/1152783005/diff/1/lib/runtime/dart_runtime.js
File lib/runtime/dart_runtime.js (left):

https://codereview.chromium.org/1152783005/diff/1/lib/runtime/dart_runtime.js...
lib/runtime/dart_runtime.js:29: function formalParameterList(fn) {
On 2015/05/29 23:02:20, John Messerly wrote:
> dead code

We may want this for parameter mirrors - otherwise, we'd need to store in
metadata I think - but I can add back if needed.  It needs to be updated for ES6
function variants anyway.

[Jennifer Messerly, 2015-06-01 16:32:43]

Committed patchset #1 (id:1) manually as
1ed893095df96a2b090bbb574919c09c5a3f719d (presubmit successful).