Update V8 to r5425 as required by WebKit r67178

Change-Id: Ic338e7242d33e5a024bd5978f4a5a3a681af4ebd
diff --git a/src/d8.cc b/src/d8.cc
index 7fd7925..5a1e63a 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -486,7 +486,7 @@
 
   // Start the debugger agent if requested.
   if (i::FLAG_debugger_agent) {
-    v8::Debug::EnableAgent("d8 shell", i::FLAG_debugger_port);
+    v8::Debug::EnableAgent("d8 shell", i::FLAG_debugger_port, true);
   }
 
   // Start the in-process debugger if requested.