Rename JdwpLocation.idx to the more intention-revealing dex_pc.

Change-Id: Ie111b1e715b701da528b0e6de87560b1eea793d1
diff --git a/src/jdwp/jdwp.h b/src/jdwp/jdwp.h
index a3f4b69..d297f6f 100644
--- a/src/jdwp/jdwp.h
+++ b/src/jdwp/jdwp.h
@@ -76,7 +76,7 @@
   JdwpTypeTag typeTag;
   RefTypeId classId;
   MethodId methodId;
-  uint64_t idx; // A Dex PC.
+  uint64_t dex_pc;
 };
 std::ostream& operator<<(std::ostream& os, const JdwpLocation& rhs);
 bool operator==(const JdwpLocation& lhs, const JdwpLocation& rhs);