Only create ScopeInfos for scopes that really need one

R=verwaest@chromium.org,marja@chromium.org

Review-Url: https://codereview.chromium.org/2351823005
Cr-Commit-Position: refs/heads/master@{#39546}

src/ast/scopes.cc

@@ -1043,6 +1043,13 @@ void DeclarationScope::AllocateVariables(ParseInfo* info, AnalyzeMode mode) {
     break;
   }
   AllocateScopeInfosRecursively(info->isolate(), mode, outer_scope);
+  // The debugger expects all shared function infos to contain a scope info.
+  // Since the top-most scope will end up in a shared function info, make sure
+  // it has one, even if it doesn't need a scope info.
+  // TODO(jochen|yangguo): Remove this requirement.
+  if (scope_info_.is_null()) {
+    scope_info_ = ScopeInfo::Create(info->isolate(), zone(), this, outer_scope);
+  }
 }
 
 bool Scope::AllowsLazyParsing() const {

src/ast/scopes.h

@@ -444,8 +444,10 @@ class Scope: public ZoneObject {
     // A lazily parsed scope doesn't contain enough information to create a
     // ScopeInfo from it.
     if (is_lazily_parsed_) return false;
-    return NeedsContext() || is_script_scope() || is_function_scope() ||
-           is_eval_scope() || is_module_scope();
+    // The debugger expects all functions to have scope infos.
+    // TODO(jochen|yangguo): Remove this requirement.
+    if (is_function_scope()) return true;
+    return NeedsContext();
   }
 
   Zone* zone_;