Simplify some code related to x64 calling convention.

R=mvstanton@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/13940014

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14409 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix segmentation fault in CodeMap::Print

CodeEntry* is always NULL for SharedFunctionInfo entries in the CodeMap. Take this into account when printing the map.

Drive-by: removed  CodeEntry::shared_id() which is never called.

BUG=None

Review URL: https://codereview.chromium.org/14387004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14410 ce2b1a6d-e550-0410-aec6-3dcde31c8c00