Fix for 2367397 - Runtime reset with threshold lowered to 20.

This was a bug in the def tracking - or more specifically neglecting to
reset tracking at a possible rollback location.
diff --git a/vm/compiler/codegen/arm/CodegenCommon.c b/vm/compiler/codegen/arm/CodegenCommon.c
index 9d2f78a..c3fa8c3 100644
--- a/vm/compiler/codegen/arm/CodegenCommon.c
+++ b/vm/compiler/codegen/arm/CodegenCommon.c
@@ -329,6 +329,9 @@
                               ArmLIR *branch,
                               ArmLIR *pcrLabel)
 {
+    /* Forget all def info (because we might rollback here.  Bug #2367397 */
+    resetDefTracking(cUnit);
+
     /* Set up the place holder to reconstruct this Dalvik PC */
     if (pcrLabel == NULL) {
         int dPC = (int) (cUnit->method->insns + dOffset);