Add RSB instruction to the ARM integrated assembler.

src/DartARM32/assembler_arm.h

Index: src/DartARM32/assembler_arm.h
diff --git a/src/DartARM32/assembler_arm.h b/src/DartARM32/assembler_arm.h
index ddf1c5f1d83ff3296c46e46c3488c22a2f0c45ef..a2426c00d15db2d68c5cacf0da624f7a3bf65386 100644
--- a/src/DartARM32/assembler_arm.h
+++ b/src/DartARM32/assembler_arm.h
@@ -459,12 +459,11 @@ class Assembler : public ValueObject {
   // Moved to ARM32::AssemberARM32::sub()
   void sub(Register rd, Register rn, Operand o, Condition cond = AL);
   void subs(Register rd, Register rn, Operand o, Condition cond = AL);
-#endif
 
+  // Moved to ARM32::AssemberARM32::rsb()
   void rsb(Register rd, Register rn, Operand o, Condition cond = AL);
   void rsbs(Register rd, Register rn, Operand o, Condition cond = AL);
 
-#if 0
   // Moved to ARM32::AssemblerARM32::add()
   void add(Register rd, Register rn, Operand o, Condition cond = AL);