Remove unreachable code from the code generator.

Remove unreachable code from the code generator.

The case of constant array bounds check can only occur for the
overflow case. Otherwise, the compiler eliminates those checks
already before code generation.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=35793

[Florian Schneider, 2014-05-05 16:02:38]

Srdjan, do you remember which test was failing at the point? The code seems to
work fine now with the code removed.

[srdjan, 2014-05-05 16:06:41]

LGTM

Unfortunately I did not write in the comments which tests were failing, and of
course I do not remember :-(. Make sure you run all the tests with
--vm-options=--optimziation-counter-threshold=5

[Florian Schneider, 2014-05-06 09:23:29]

Committed patchset #1 manually as r35793 (presubmit successful).