Update V8 to r5091 as required by WebKit r63859.

Change-Id: I8e35d765e6f6c7f89eccff900e1cabe2d5dd6110
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index 0b5ff99..d340e4b 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -789,6 +789,7 @@
   CHECK(IsSharedFunctionInfo());
   VerifyObjectField(kNameOffset);
   VerifyObjectField(kCodeOffset);
+  VerifyObjectField(kScopeInfoOffset);
   VerifyObjectField(kInstanceClassNameOffset);
   VerifyObjectField(kFunctionDataOffset);
   VerifyObjectField(kScriptOffset);