When specifying a new create histogram callback, reset all histograms so they recreate themselves on next use.

We only do this for histograms, and not for counters, as counters might be used directly from generated code

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/10828113
Patch from Jochen Eisinger <jochen@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12248 ce2b1a6d-e550-0410-aec6-3dcde31c8c00