Put code flushing behind flag - defaults to false.

Since we have an issue with code flusing on the trybots preventing us
from pushing to chromium, a new flag for enabling code flushing,
--flush_code, is introduced with this change (defaulting to false).

Review URL: http://codereview.chromium.org/2734005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4840 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -191,6 +191,8 @@ DEFINE_bool(trace_gc_verbose, false,
             "print more details following each garbage collection")
 DEFINE_bool(collect_maps, true,
             "garbage collect maps from which no objects can be reached")
+DEFINE_bool(flush_code, false,
+            "flush code that we expect not to use again before full gc")
 
 // v8.cc
 DEFINE_bool(use_idle_notification, true,

src/heap.cc

@@ -605,8 +605,10 @@ void Heap::PerformGarbageCollection(AllocationSpace space,
   EnsureFromSpaceIsCommitted();
 
   if (collector == MARK_COMPACTOR) {
-    // Flush all potentially unused code.
-    FlushCode();
+    if (FLAG_flush_code) {
+      // Flush all potentially unused code.
+      FlushCode();
+    }
 
     // Perform mark-sweep with optional compaction.
     MarkCompact(tracer);