Update V8 to r4851 as required by WebKit r61121

Change-Id: Ib01b7c8e38d5b82b254192fc06365aa5b85780c5
diff --git a/src/compiler.cc b/src/compiler.cc
index ca92ed9..ebb9743 100755
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -601,6 +601,7 @@
       lit->has_only_simple_this_property_assignments(),
       *lit->this_property_assignments());
   function_info->set_try_full_codegen(lit->try_full_codegen());
+  function_info->set_allows_lazy_compilation(lit->AllowsLazyCompilation());
 }