Fix rounding in Uint8ClampedArray setter.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 83aef7801a70bc663815a9270b61eb5b9df33af1..e81144a244abccd94fcf33c0f5d243dfda03dcd1 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -134,10 +134,7 @@ void MacroAssembler::ClampDoubleToUint8(XMMRegister input_reg,
   Set(result_reg, Immediate(0));
   ucomisd(input_reg, scratch_reg);
   j(below, &done, Label::kNear);
-  ExternalReference half_ref = ExternalReference::address_of_one_half();
-  movdbl(scratch_reg, Operand::StaticVariable(half_ref));
-  addsd(scratch_reg, input_reg);
-  cvttsd2si(result_reg, Operand(scratch_reg));
+  cvtsd2si(result_reg, input_reg);
   test(result_reg, Immediate(0xFFFFFF00));
   j(zero, &done, Label::kNear);
   Set(result_reg, Immediate(255));