Update V8 to r5780 as required by WebKit r71558

Change-Id: Ie3936550b99967a13755930d0dac0a59c3562625
diff --git a/src/objects.h b/src/objects.h
index 87234ea..6029ad5 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -3409,8 +3409,7 @@
   // Script compilation types.
   enum CompilationType {
     COMPILATION_TYPE_HOST = 0,
-    COMPILATION_TYPE_EVAL = 1,
-    COMPILATION_TYPE_JSON = 2
+    COMPILATION_TYPE_EVAL = 1
   };
 
   // [source]: the script source.