Use the code patcher for the patching of the JS return sequence used by the debugger.

Added explicit instruction cache flushing in a code patching section which did not have it for completeness, even though it is not required on Intel processors.
Review URL: http://codereview.chromium.org/203016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2870 ce2b1a6d-e550-0410-aec6-3dcde31c8c00