Add vrint{a,n,p,m,z} instructions to arm assembler.

src/arm/assembler-arm.h

Index: src/arm/assembler-arm.h
diff --git a/src/arm/assembler-arm.h b/src/arm/assembler-arm.h
index f78cc50b38f9e7d374057619e4b2f72df1c8caf6..9087fab56a41b6fe2f2ff24f5bae1a74613355fa 100644
--- a/src/arm/assembler-arm.h
+++ b/src/arm/assembler-arm.h
@@ -1279,6 +1279,14 @@ class Assembler : public AssemblerBase {
              const DwVfpRegister src,
              const Condition cond = al);
 
+  // ARMv8 rounding instructions.
+  void vrinta(const DwVfpRegister dst, const DwVfpRegister src);
+  void vrintn(const DwVfpRegister dst, const DwVfpRegister src);
+  void vrintm(const DwVfpRegister dst, const DwVfpRegister src);
+  void vrintp(const DwVfpRegister dst, const DwVfpRegister src);
+  void vrintz(const DwVfpRegister dst, const DwVfpRegister src,
+              const Condition cond = al);
+
   // Support for NEON.
   // All these APIs support D0 to D31 and Q0 to Q15.