VM: Use canonical empty-array for empty inlining meta-data.

VM: Use canonical empty-array for empty inlining meta-data.

When inlining meta-information is not used, use Object::empty_array()
instead of Array::New(0), thus saving those allocations.

Guard places for length 0 - before all code objects had an inlining
interval array of length at least 1.

This saves 2 old-space array allocations per unoptimized code object.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=45435

[Florian Schneider, 2015-04-24 13:15:51]

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

[Florian Schneider, 2015-04-24 13:15:52]

+john for observatory test changes.

[srdjan, 2015-04-24 15:38:07]

lgtm

[Florian Schneider, 2015-04-27 22:50:11]

Committed patchset #3 (id:40001) manually as r45435 (presubmit successful).