[serializer] Move clearing of optimized code map out of GC.

This avoids the need to clear optimized code maps within the GC by just
preventing entries being added in the first place, whenever a snapshot
is being constructed. The main goal here is to simplify the logic in the
already complex visitor for our shared function info objects.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1411513005

Cr-Commit-Position: refs/heads/master@{#31852}

src/heap/objects-visiting-inl.h

@@ -443,8 +443,7 @@ void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfo(
   if (FLAG_cleanup_code_caches_at_gc) {
     shared->ClearTypeFeedbackInfoAtGCTime();
   }
-  if ((FLAG_flush_optimized_code_cache ||
-       heap->isolate()->serializer_enabled()) &&
+  if (FLAG_flush_optimized_code_cache &&
       !shared->optimized_code_map()->IsSmi()) {
     // Always flush the optimized code map if requested by flag.
     shared->ClearOptimizedCodeMap();

src/objects.cc

@@ -11035,6 +11035,7 @@ void JSFunction::AttemptConcurrentOptimization() {
 void SharedFunctionInfo::AddSharedCodeToOptimizedCodeMap(
     Handle<SharedFunctionInfo> shared, Handle<Code> code) {
   Isolate* isolate = shared->GetIsolate();
+  if (isolate->serializer_enabled()) return;
   DCHECK(code->kind() == Code::OPTIMIZED_FUNCTION);
   Handle<Object> value(shared->optimized_code_map(), isolate);
   if (value->IsSmi()) return;  // Empty code maps are unsupported.
@@ -11048,6 +11049,7 @@ void SharedFunctionInfo::AddToOptimizedCodeMap(
     Handle<HeapObject> code, Handle<LiteralsArray> literals,
     BailoutId osr_ast_id) {
   Isolate* isolate = shared->GetIsolate();
+  if (isolate->serializer_enabled()) return;
   DCHECK(*code == isolate->heap()->undefined_value() ||
          !shared->SearchOptimizedCodeMap(*native_context, osr_ast_id).code);
   DCHECK(*code == isolate->heap()->undefined_value() ||