[ast] Never declare non-lexical variables as kNeedsInitialization.

R=adamk@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2232343002
Cr-Commit-Position: refs/heads/master@{#38589}

src/ast/scopes.cc

@@ -1249,9 +1249,9 @@ Variable* Scope::NonLocal(const AstRawString* name, VariableMode mode) {
   Variable* var = map->Lookup(name);
   if (var == NULL) {
     // Declare a new non-local.
-    InitializationFlag init_flag = (mode == VAR)
-        ? kCreatedInitialized : kNeedsInitialization;
-    var = map->Declare(zone(), NULL, name, mode, Variable::NORMAL, init_flag);
+    DCHECK(!IsLexicalVariableMode(mode));
+    var = map->Declare(zone(), NULL, name, mode, Variable::NORMAL,
+                       kCreatedInitialized);
     // Allocate it by giving it a dynamic lookup.
     var->AllocateTo(VariableLocation::LOOKUP, -1);
   }

src/ast/variables.h

@@ -73,6 +73,8 @@ class Variable: public ZoneObject {
   bool is_dynamic() const { return IsDynamicVariableMode(mode_); }
   bool is_const_mode() const { return IsImmutableVariableMode(mode_); }
   bool binding_needs_init() const {
+    DCHECK(initialization_flag_ != kNeedsInitialization ||
+           IsLexicalVariableMode(mode_));
     return initialization_flag_ == kNeedsInitialization;
   }