[es6] Partially implement Reflect.preventExtensions.

src/isolate.h

 // 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.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include <queue>
 #include <set>
 
@@ skipping 146 matching lines @@
     }                                                              \
   } while (false)
 
 #define RETURN_FAILURE_ON_EXCEPTION(isolate, call)  \
   RETURN_ON_EXCEPTION_VALUE(isolate, call, isolate->heap()->exception())
 
 #define RETURN_ON_EXCEPTION(isolate, call, T)  \
   RETURN_ON_EXCEPTION_VALUE(isolate, call, MaybeHandle<T>())
 
 
+// Macros for Maybe.
+
+#define MAYBE_ASSIGN_RETURN_ON_EXCEPTION(isolate, T, dst, call) \
+  do {                                                          \
+    Maybe<T> result_of_the_call = (call);                       \
+    if (result_of_the_call.IsNothing()) {                       \
+      DCHECK((isolate)->has_pending_exception());               \
+      return isolate->heap()->exception();                      \
+    }                                                           \
+    (dst) = result_of_the_call.FromJust();                      \
+  } while (false)
+
+
 #define FOR_EACH_ISOLATE_ADDRESS_NAME(C)                \
   C(Handler, handler)                                   \
   C(CEntryFP, c_entry_fp)                               \
   C(CFunction, c_function)                              \
   C(Context, context)                                   \
   C(PendingException, pending_exception)                \
   C(PendingHandlerContext, pending_handler_context)     \
   C(PendingHandlerCode, pending_handler_code)           \
   C(PendingHandlerOffset, pending_handler_offset)       \
   C(PendingHandlerFP, pending_handler_fp)               \
@@ skipping 1379 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_