Merge (x & y) == 0 pattern to emit a single test instruction.

runtime/vm/assembler_arm.h

Index: runtime/vm/assembler_arm.h
===================================================================
--- runtime/vm/assembler_arm.h	(revision 29964)
+++ runtime/vm/assembler_arm.h	(working copy)
@@ -585,9 +585,13 @@
 
   void AndImmediate(Register rd, Register rs, int32_t imm, Condition cond = AL);
 
+  // Test rn and immediate. May clobber IP.
+  void TestImmediate(Register rn, int32_t imm, Condition cond = AL);
+
   // Compare rn with signed immediate value. May clobber IP.
   void CompareImmediate(Register rn, int32_t value, Condition cond = AL);
 
+
   // Signed integer division of left by right. Checks to see if integer
   // division is supported. If not, uses the FPU for division with
   // temporary registers tmpl and tmpr. tmpl and tmpr must be different