Handle filling up of memory buffer to make log processing in DevTools Profiler easier.

Handle filling up of memory buffer to make log processing in DevTools Profiler easier.

When profiler's memory buffer is filled up, profiling is stopped and it is ensured that the last record in the buffer is "profiler,\"pause\"" thus making the end of profiling session explicit. Otherwise DevTools Profiler would need to guess whether the current profiling session has been stopped.

Tested with Chromium.

Review URL: http://codereview.chromium.org/115859

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2072 ce2b1a6d-e550-0410-aec6-3dcde31c8c00