Revert change to const and global variable declarations. It causes

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index a6670bf718795e7069b5198fa8b0493614fa3846..48ff69f5d273071e0615743e2b2760f2abb71e70 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -1051,12 +1051,6 @@ static MaybeObject* Runtime_DeclareGlobals(Arguments args) {
           // Fall-through and introduce the absent property by using
           // SetProperty.
         } else {
-          // For const properties, we treat a callback with this name
-          // even in the prototype as a conflicting declaration.
-          if (is_const_property && (lookup.type() == CALLBACKS)) {
-            return ThrowRedeclarationError("const", name);
-          }
-          // Otherwise, we check for locally conflicting declarations.
           if (is_local && (is_read_only || is_const_property)) {
             const char* type = (is_read_only) ? "const" : "var";
             return ThrowRedeclarationError(type, name);
@@ -1082,20 +1076,30 @@ static MaybeObject* Runtime_DeclareGlobals(Arguments args) {
         ? static_cast<PropertyAttributes>(base | READ_ONLY)
         : base;
 
-    // There's a local property that we need to overwrite because
-    // we're either declaring a function or there's an interceptor
-    // that claims the property is absent.
-    //
-    // Check for conflicting re-declarations. We cannot have
-    // conflicting types in case of intercepted properties because
-    // they are absent.
-    if (lookup.IsProperty() &&
-        (lookup.type() != INTERCEPTOR) &&
-        (lookup.IsReadOnly() || is_const_property)) {
-      const char* type = (lookup.IsReadOnly()) ? "const" : "var";
-      return ThrowRedeclarationError(type, name);
+    if (lookup.IsProperty()) {
+      // There's a local property that we need to overwrite because
+      // we're either declaring a function or there's an interceptor
+      // that claims the property is absent.
+
+      // Check for conflicting re-declarations. We cannot have
+      // conflicting types in case of intercepted properties because
+      // they are absent.
+      if (lookup.type() != INTERCEPTOR &&
+          (lookup.IsReadOnly() || is_const_property)) {
+        const char* type = (lookup.IsReadOnly()) ? "const" : "var";
+        return ThrowRedeclarationError(type, name);
+      }
+      RETURN_IF_EMPTY_HANDLE(SetProperty(global, name, value, attributes));
+    } else {
+      // If a property with this name does not already exist on the
+      // global object add the property locally.  We take special
+      // precautions to always add it as a local property even in case
+      // of callbacks in the prototype chain (this rules out using
+      // SetProperty).  Also, we must use the handle-based version to
+      // avoid GC issues.
+      RETURN_IF_EMPTY_HANDLE(
+          SetLocalPropertyIgnoreAttributes(global, name, value, attributes));
     }
-    RETURN_IF_EMPTY_HANDLE(SetProperty(global, name, value, attributes));
   }
 
   ASSERT(!Top::has_pending_exception());
@@ -1182,20 +1186,6 @@ static MaybeObject* Runtime_DeclareContextSlot(Arguments args) {
     ASSERT(!context_ext->HasLocalProperty(*name));
     Handle<Object> value(Heap::undefined_value());
     if (*initial_value != NULL) value = initial_value;
-    // Declaring a const context slot is a conflicting declaration if
-    // there is a callback with that name in a prototype. It is
-    // allowed to introduce const variables in
-    // JSContextExtensionObjects. They are treated specially in
-    // SetProperty and no setters are invoked for those since they are
-    // not real JSObjects.
-    if (initial_value->IsTheHole() &&
-        !context_ext->IsJSContextExtensionObject()) {
-      LookupResult lookup;
-      context_ext->Lookup(*name, &lookup);
-      if (lookup.IsProperty() && (lookup.type() == CALLBACKS)) {
-        return ThrowRedeclarationError("const", name);
-      }
-    }
     RETURN_IF_EMPTY_HANDLE(SetProperty(context_ext, name, value, mode));
   }
 
@@ -1222,7 +1212,11 @@ static MaybeObject* Runtime_InitializeVarGlobal(Arguments args) {
   // there, there is a property with this name in the prototype chain.
   // We follow Safari and Firefox behavior and only set the property
   // locally if there is an explicit initialization value that we have
-  // to assign to the property.
+  // to assign to the property. When adding the property we take
+  // special precautions to always add it as a local property even in
+  // case of callbacks in the prototype chain (this rules out using
+  // SetProperty).  We have SetLocalPropertyIgnoreAttributes for
+  // this.
   // Note that objects can have hidden prototypes, so we need to traverse
   // the whole chain of hidden prototypes to do a 'local' lookup.
   JSObject* real_holder = global;
@@ -1283,7 +1277,11 @@ static MaybeObject* Runtime_InitializeVarGlobal(Arguments args) {
   }
 
   global = Top::context()->global();
-  if (assign) return global->SetProperty(*name, args[1], attributes);
+  if (assign) {
+    return global->SetLocalPropertyIgnoreAttributes(*name,
+                                                    args[1],
+                                                    attributes);
+  }
   return Heap::undefined_value();
 }