Simplify stack trace getter wrt prototype chain walk.

src/messages.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // -------------------------------------------------------------------
 
 var kMessages = {
   // Error
   cyclic_proto:                  ["Cyclic __proto__ value"],
   code_gen_from_strings:         ["%0"],
@@ skipping 1105 matching lines @@
 
 var stack_trace_symbol;  // Set during bootstrapping.
 var formatted_stack_trace_symbol = NEW_PRIVATE_OWN("formatted stack trace");
 
 
 // Format the stack trace if not yet done, and return it.
 // Cache the formatted stack trace on the holder.
 var StackTraceGetter = function() {
   var formatted_stack_trace = UNDEFINED;
   var holder = this;
-  while (holder && IS_UNDEFINED(formatted_stack_trace)) {
-    formatted_stack_trace = GET_PRIVATE(holder, formatted_stack_trace_symbol);
-    holder = %GetPrototype(holder);
+  while (holder) {
+    var formatted_stack_trace =
+      GET_PRIVATE(holder, formatted_stack_trace_symbol);

[arv (Not doing code reviews), 2014/09/24 14:15:17]

wrong indent

+    if (IS_UNDEFINED(formatted_stack_trace)) {
+      // No formatted stack trace available.
+      var stack_trace = GET_PRIVATE(holder, stack_trace_symbol);
+      if (IS_UNDEFINED(stack_trace)) {
+        // Neither formatted nor structured stack trace available.
+        // Look further up the prototype chain.
+        holder = %GetPrototype(holder);
+        continue;
+      }
+      formatted_stack_trace = FormatStackTrace(holder, stack_trace);
+      SET_PRIVATE(holder, stack_trace_symbol, UNDEFINED);
+      SET_PRIVATE(holder, formatted_stack_trace_symbol, formatted_stack_trace);
+    }
+    return formatted_stack_trace;
   }
-  if (IS_UNDEFINED(formatted_stack_trace)) {
-    holder = this;
-    while (!HAS_DEFINED_PRIVATE(holder, stack_trace_symbol)) {
-      holder = %GetPrototype(holder);
-      if (!holder) return UNDEFINED;
-    }
-    var stack_trace = GET_PRIVATE(holder, stack_trace_symbol);
-    if (IS_UNDEFINED(stack_trace)) return UNDEFINED;
-    formatted_stack_trace = FormatStackTrace(holder, stack_trace);
-    SET_PRIVATE(holder, stack_trace_symbol, UNDEFINED);
-    SET_PRIVATE(holder, formatted_stack_trace_symbol, formatted_stack_trace);
-  }
-  return formatted_stack_trace;
+  return UNDEFINED;
 };
 
 
 // If the receiver equals the holder, set the formatted stack trace that the
 // getter returns.
 var StackTraceSetter = function(v) {
   if (HAS_PRIVATE(this, stack_trace_symbol)) {
     SET_PRIVATE(this, stack_trace_symbol, UNDEFINED);
     SET_PRIVATE(this, formatted_stack_trace_symbol, v);
   }
@@ skipping 143 matching lines @@
 function SetUpStackOverflowBoilerplate() {
   var boilerplate = MakeRangeError('stack_overflow', []);
 
   %DefineAccessorPropertyUnchecked(
       boilerplate, 'stack', StackTraceGetter, StackTraceSetter, DONT_ENUM);
 
   return boilerplate;
 }
 
 var kStackOverflowBoilerplate = SetUpStackOverflowBoilerplate();