Fix liveedit heap traversal bug with write barrier

Review URL: https://chromiumcodereview.appspot.com/10639006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11927 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/liveedit.cc

@@ -968,6 +968,14 @@ class ReplacingVisitor : public ObjectVisitor {
 static void ReplaceCodeObject(Code* original, Code* substitution) {
   ASSERT(!HEAP->InNewSpace(substitution));
 
+  // Perform a full GC in order to ensure that we are not in the middle of an
+  // incremental marking phase when we are replacing the code object.
+  // Since we are not in an incremental marking phase we can write pointers
+  // to code objects (that are never in new space) without worrying about
+  // write barriers.
+  HEAP->CollectAllGarbage(Heap::kMakeHeapIterableMask,
+                          "liveedit.cc ReplaceCodeObject");
+
   AssertNoAllocation no_allocations_please;
 
   ReplacingVisitor visitor(original, substitution);