Reapply "Support for precise stepping in functions compiled before debugging was...

Reapply "Support for precise stepping in functions compiled before debugging was started (step 2)"

This is reapplying r9501 with this single change which seemed to be causing most (all) of the failures for r9501.

--- a/src/debug.cc
+++ b/src/debug.cc
@@ -2230,6 +2230,7 @@ Debugger::Debugger(Isolate* isolate)
       compiling_natives_(false),
       is_loading_debugger_(false),
       never_unload_debugger_(false),
+      force_debugger_active_(true),
       message_handler_(NULL),
       debugger_unload_pending_(false),
       host_dispatch_handler_(NULL),

R=kmillikin@chromium.org

BUG=
TEST=

Review URL: http://codereview.chromium.org//8337009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9684 ce2b1a6d-e550-0410-aec6-3dcde31c8c00