Inline Doubles truncate and round.

runtime/vm/assembler_ia32.h

Index: runtime/vm/assembler_ia32.h
===================================================================
--- runtime/vm/assembler_ia32.h	(revision 16975)
+++ runtime/vm/assembler_ia32.h	(working copy)
@@ -400,6 +400,14 @@
 
   void pxor(XmmRegister dst, XmmRegister src);
 
+  enum RoundingMode {
+    kRoundToNearest = 0x0,
+    kRoundDown      = 0x1,
+    kRoundUp        = 0x2,
+    kRoundToZero    = 0x3
+  };
+  void roundsd(XmmRegister dst, XmmRegister src, RoundingMode mode);
+
   void flds(const Address& src);
   void fstps(const Address& dst);
 
@@ -561,6 +569,7 @@
   void FloatNegate(XmmRegister f);
 
   void DoubleAbs(XmmRegister reg);
+  void DoubleRound(XmmRegister dst, XmmRegister src, XmmRegister tmp);
 
   void LockCmpxchgl(const Address& address, Register reg) {
     lock();