Update V8 to r3431 as required by WebKit r51976.

Change-Id: I567392c3f8c0a0d5201a4249611ac4ccf468cd5b
diff --git a/src/assembler.h b/src/assembler.h
index 21a66dd..aecd4cd 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -373,6 +373,8 @@
  public:
   explicit ExternalReference(Builtins::CFunctionId id);
 
+  explicit ExternalReference(ApiFunction* ptr);
+
   explicit ExternalReference(Builtins::Name name);
 
   explicit ExternalReference(Runtime::FunctionId id);
@@ -406,7 +408,10 @@
   static ExternalReference roots_address();
 
   // Static variable StackGuard::address_of_jslimit()
-  static ExternalReference address_of_stack_guard_limit();
+  static ExternalReference address_of_stack_limit();
+
+  // Static variable StackGuard::address_of_real_jslimit()
+  static ExternalReference address_of_real_stack_limit();
 
   // Static variable RegExpStack::limit_address()
   static ExternalReference address_of_regexp_stack_limit();
@@ -422,6 +427,12 @@
   static ExternalReference double_fp_operation(Token::Value operation);
   static ExternalReference compare_doubles();
 
+  static ExternalReference handle_scope_extensions_address();
+  static ExternalReference handle_scope_next_address();
+  static ExternalReference handle_scope_limit_address();
+
+  static ExternalReference scheduled_exception_address();
+
   Address address() const {return reinterpret_cast<Address>(address_);}
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
@@ -460,12 +471,16 @@
 
   static void* Redirect(void* address, bool fp_return = false) {
     if (redirector_ == NULL) return address;
-    return (*redirector_)(address, fp_return);
+    void* answer = (*redirector_)(address, fp_return);
+    return answer;
   }
 
   static void* Redirect(Address address_arg, bool fp_return = false) {
     void* address = reinterpret_cast<void*>(address_arg);
-    return redirector_ == NULL ? address : (*redirector_)(address, fp_return);
+    void* answer = (redirector_ == NULL) ?
+                   address :
+                   (*redirector_)(address, fp_return);
+    return answer;
   }
 
   void* address_;