When loaded scripts are requested this cache is filled with all the script objects in the heap. Hereafter its content is kept in sync with the active scripts in the heap through the notifications of new scripts compiled and by using weak handles to get notified when a script is collected.

Through the tracking of collected scripts the debugger event OnScriptCollected have been added to notify a debugger that a script previously returned through the scripts command is no longer in use.

Make the ComputeIntegerHash globally available.

Moved clearing of the mirror cache to when debugger is really left. Previously recursive invocations of the debugger cause the mirror cache to be cleared causing handles to become either stale or reference other objects.
Review URL: http://codereview.chromium.org/115462

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1988 ce2b1a6d-e550-0410-aec6-3dcde31c8c00