Uses a conditional move for usage counter increment instead of a branch

runtime/vm/assembler_ia32.cc

Index: runtime/vm/assembler_ia32.cc
===================================================================
--- runtime/vm/assembler_ia32.cc	(revision 38122)
+++ runtime/vm/assembler_ia32.cc	(working copy)
@@ -273,6 +273,15 @@
 }
 
 
+// Move if not overflow.
+void Assembler::cmovno(Register dst, Register src) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitUint8(0x0F);
+  EmitUint8(0x41);
+  EmitRegisterOperand(dst, src);
+}
+
+
 void Assembler::cmove(Register dst, Register src) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitUint8(0x0F);