Revert of Always deserialize scope infos for parsing

src/ast/scopeinfo.cc

Index: src/ast/scopeinfo.cc
diff --git a/src/ast/scopeinfo.cc b/src/ast/scopeinfo.cc
index c5c771f595a92e65b981c58d4cd46c81e2f3605d..a9e824f415bae54881eb5dc84c3787905418756c 100644
--- a/src/ast/scopeinfo.cc
+++ b/src/ast/scopeinfo.cc
@@ -4,6 +4,7 @@
 
 #include <stdlib.h>
 
+#include "src/ast/context-slot-cache.h"
 #include "src/ast/scopes.h"
 #include "src/bootstrapper.h"
 
@@ -478,6 +479,15 @@
   DCHECK_NOT_NULL(maybe_assigned_flag);
 
   if (scope_info->length() > 0) {
+    ContextSlotCache* context_slot_cache =
+        scope_info->GetIsolate()->context_slot_cache();
+    int result = context_slot_cache->Lookup(*scope_info, *name, mode, init_flag,
+                                            maybe_assigned_flag);
+    if (result != ContextSlotCache::kNotFound) {
+      DCHECK(result < scope_info->ContextLength());
+      return result;
+    }
+
     int start = scope_info->ContextLocalNameEntriesIndex();
     int end = start + scope_info->ContextLocalCount();
     for (int i = start; i < end; ++i) {
@@ -486,11 +496,17 @@
         *mode = scope_info->ContextLocalMode(var);
         *init_flag = scope_info->ContextLocalInitFlag(var);
         *maybe_assigned_flag = scope_info->ContextLocalMaybeAssignedFlag(var);
-        int result = Context::MIN_CONTEXT_SLOTS + var;
+        result = Context::MIN_CONTEXT_SLOTS + var;
+
+        context_slot_cache->Update(scope_info, name, *mode, *init_flag,
+                                   *maybe_assigned_flag, result);
         DCHECK(result < scope_info->ContextLength());
         return result;
       }
     }
+    // Cache as not found. Mode, init flag and maybe assigned flag don't matter.
+    context_slot_cache->Update(scope_info, name, TEMPORARY,
+                               kNeedsInitialization, kNotAssigned, -1);
   }
 
   return -1;