Update V8 to r5388 as required by WebKit r66666

Change-Id: Ib3c42e9b7226d22c65c7077c543fe31afe62a318
diff --git a/src/builtins.h b/src/builtins.h
index 375e8f3..7e49f31 100644
--- a/src/builtins.h
+++ b/src/builtins.h
@@ -117,7 +117,10 @@
   V(FunctionApply,              BUILTIN, UNINITIALIZED)                   \
                                                                           \
   V(ArrayCode,                  BUILTIN, UNINITIALIZED)                   \
-  V(ArrayConstructCode,         BUILTIN, UNINITIALIZED)
+  V(ArrayConstructCode,         BUILTIN, UNINITIALIZED)                   \
+                                                                          \
+  V(StringConstructCode,        BUILTIN, UNINITIALIZED)
+
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
 // Define list of builtins used by the debugger implemented in assembly.
@@ -258,6 +261,8 @@
 
   static void Generate_ArrayCode(MacroAssembler* masm);
   static void Generate_ArrayConstructCode(MacroAssembler* masm);
+
+  static void Generate_StringConstructCode(MacroAssembler* masm);
 };
 
 } }  // namespace v8::internal