Zap map value in the stub-cache on clear.

The empty_string is a valid key for keyed loads and stores.

BUG=
R=mstarzinger@chromium.org

Review URL: https://chromiumcodereview.appspot.com/15565002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14732 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/stub-cache.cc

@@ -1034,10 +1034,12 @@ void StubCache::Clear() {
   Code* empty = isolate_->builtins()->builtin(Builtins::kIllegal);
   for (int i = 0; i < kPrimaryTableSize; i++) {
     primary_[i].key = heap()->empty_string();
+    primary_[i].map = NULL;
     primary_[i].value = empty;
   }
   for (int j = 0; j < kSecondaryTableSize; j++) {
     secondary_[j].key = heap()->empty_string();
+    secondary_[j].map = NULL;
     secondary_[j].value = empty;
   }
 }