Generate Nops to ensure that debug stack maps have distinct PC.

Change-Id: I5740ec958a20d236634b66df0e675382ed5c16fc
diff --git a/compiler/optimizing/code_generator.h b/compiler/optimizing/code_generator.h
index eade05d..950043e 100644
--- a/compiler/optimizing/code_generator.h
+++ b/compiler/optimizing/code_generator.h
@@ -269,6 +269,8 @@
 
   // Record native to dex mapping for a suspend point.  Required by runtime.
   void RecordPcInfo(HInstruction* instruction, uint32_t dex_pc, SlowPathCode* slow_path = nullptr);
+  // Check whether we have already recorded mapping at this PC.
+  bool HasStackMapAtCurrentPc();
 
   bool CanMoveNullCheckToUser(HNullCheck* null_check);
   void MaybeRecordImplicitNullCheck(HInstruction* instruction);