Update V8 to r6768 as required by WebKit r78450

Change-Id: Ib8868ff7147a76547a8d1d85f257ebe8546a3d3f
diff --git a/src/ia32/macro-assembler-ia32.h b/src/ia32/macro-assembler-ia32.h
index 6f180c6..09584f7 100644
--- a/src/ia32/macro-assembler-ia32.h
+++ b/src/ia32/macro-assembler-ia32.h
@@ -258,6 +258,17 @@
     j(not_carry, is_smi);
   }
 
+  // Jump the register contains a smi.
+  inline void JumpIfSmi(Register value, Label* smi_label) {
+    test(value, Immediate(kSmiTagMask));
+    j(zero, smi_label, not_taken);
+  }
+  // Jump if register contain a non-smi.
+  inline void JumpIfNotSmi(Register value, Label* not_smi_label) {
+    test(value, Immediate(kSmiTagMask));
+    j(not_zero, not_smi_label, not_taken);
+  }
+
   // Assumes input is a heap object.
   void JumpIfNotNumber(Register reg, TypeInfo info, Label* on_not_number);
 
@@ -539,6 +550,10 @@
 
   void Ret();
 
+  // Return and drop arguments from stack, where the number of arguments
+  // may be bigger than 2^16 - 1.  Requires a scratch register.
+  void Ret(int bytes_dropped, Register scratch);
+
   // Emit code to discard a non-negative number of pointer-sized elements
   // from the stack, clobbering only the esp register.
   void Drop(int element_count);