Branch-to-self is a backward branch.

Teach the verifier to identify branch-to-self as a backward branch,
which makes the instruction a GC point and worthy of a register map.

For bug 2702514.

Change-Id: Id5b26220db8008adbb2b5b7f69894a7704a0b559
diff --git a/vm/analysis/DexVerify.c b/vm/analysis/DexVerify.c
index 9309a11..3793a4e 100644
--- a/vm/analysis/DexVerify.c
+++ b/vm/analysis/DexVerify.c
@@ -505,7 +505,7 @@
             int offset = -1;
             bool unused;
             if (dvmGetBranchTarget(meth, insnFlags, i, &offset, &unused)) {
-                if (offset < 0) {
+                if (offset <= 0) {
                     dvmInsnSetGcPoint(insnFlags, i, true);
                 }
             } else {