VM: Improve unoptimized code size by avoid emitting field guards.

VM: Improve unoptimized code size by avoid emitting field guards.

Avoid emitting field guard code for fields that have dynamic cid and/or
no fixed length. To keep unoptimized and optimized flow-graphs in sync, the
deopt-id counter has to be advanced accordingly if the guard instructions are
not emitted.

If optimizations are disabled via --noopt, do not emit any field guards and
edge counters.

R=vegorov@google.com

Committed: https://code.google.com/p/dart/source/detail?r=45502

[Florian Schneider, 2015-05-04 18:35:26]

fschneider@google.com changed reviewers:
+ vegorov@google.com

[Vyacheslav Egorov (Google), 2015-05-04 18:45:26]

lgtm

[Florian Schneider, 2015-05-04 18:46:50]

Committed patchset #2 (id:20001) manually as r45502 (presubmit successful).