Fix more JDWP bugs.

Change-Id: I475d14e196a7463e70f7cce6a8b8d77f867e9e46
diff --git a/src/debugger.h b/src/debugger.h
index b92fbfe..8a702a1 100644
--- a/src/debugger.h
+++ b/src/debugger.h
@@ -140,7 +140,7 @@
   static void FindLoadedClassBySignature(const char* descriptor, std::vector<JDWP::RefTypeId>& ids);
   static void GetObjectType(JDWP::ObjectId objectId, JDWP::JdwpTypeTag* pRefTypeTag, JDWP::RefTypeId* pRefTypeId);
   static uint8_t GetClassObjectType(JDWP::RefTypeId refTypeId);
-  static bool GetSignature(JDWP::RefTypeId refTypeId, std::string& signature);
+  static JDWP::JdwpError GetSignature(JDWP::RefTypeId refTypeId, std::string& signature);
   static bool GetSourceFile(JDWP::RefTypeId refTypeId, std::string& source_file);
   static uint8_t GetObjectTag(JDWP::ObjectId objectId);
   static size_t GetTagWidth(JDWP::JdwpTag tag);