Update V8 to r3431 as required by WebKit r51976.

Change-Id: I567392c3f8c0a0d5201a4249611ac4ccf468cd5b
diff --git a/src/x64/simulator-x64.h b/src/x64/simulator-x64.h
index 998c909..c4f3a85 100644
--- a/src/x64/simulator-x64.h
+++ b/src/x64/simulator-x64.h
@@ -44,6 +44,12 @@
   static inline uintptr_t JsLimitFromCLimit(uintptr_t c_limit) {
     return c_limit;
   }
+
+  static inline uintptr_t RegisterCTryCatch(uintptr_t try_catch_address) {
+    return try_catch_address;
+  }
+
+  static inline void UnregisterCTryCatch() { }
 };
 
 // Call the generated regexp code directly. The entry function pointer should
@@ -51,4 +57,7 @@
 #define CALL_GENERATED_REGEXP_CODE(entry, p0, p1, p2, p3, p4, p5, p6) \
   entry(p0, p1, p2, p3, p4, p5, p6)
 
+#define TRY_CATCH_FROM_ADDRESS(try_catch_address) \
+  reinterpret_cast<TryCatch*>(try_catch_address)
+
 #endif  // V8_X64_SIMULATOR_X64_H_