Fix an off-by-one error in deoptimization compression.

Fix an off-by-one error in deoptimization compression.

When compressing the deoptimization info, suffixes of length one are not
shared (the compression is the same length as the original, but more
indirect).  However, they were grafted onto the trie as if they were shared,
i.e., one level lower than they should be.

Add debug code to verify the compression/decompression round trip.

BUG=dartbug.com/13273
R=fschneider@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27602

[Kevin Millikin (Google), 2013-09-13 13:46:17]

https://codereview.chromium.org/23788012/diff/1/runtime/vm/deopt_instructions.h
File runtime/vm/deopt_instructions.h (right):

https://codereview.chromium.org/23788012/diff/1/runtime/vm/deopt_instructions...
runtime/vm/deopt_instructions.h:205: RawDeoptInfo* CreateDeoptInfo(const Array&
deopt_table);
The table gets threaded around just for verification (decompression).  I don't
see a simple way around it.

[Florian Schneider, 2013-09-16 08:08:58]

lgtm

[Kevin Millikin (Google), 2013-09-18 10:16:27]

Committed patchset #2 manually as r27602 (presubmit successful).