Fix bug with deoptimization targets.
Fix bug with deoptimization targets.

In the second pass of inserting representation conversions (SelectRepresentations)
we may insert sequences of Unbox/Box instructions that are eliminated
by canonicalization later. However, inserting conversions requires a deoptimization id as
deoptimization target. Return kNoDeoptId for Box-instructions since they don't need a real
deoptimization target.

BUG=dartbug.com/14808
R=srdjan@google.com

Review URL: https://codereview.chromium.org//71373005

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@30234 260f80e4-7a28-3924-810f-c04153c831b5

dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk