Avoid copying and strlen(3) in the FindClass path.

Change-Id: I789f3c883596d1852a2c1954ce7a207e6f937117
diff --git a/src/jdwp/jdwp_handler.cc b/src/jdwp/jdwp_handler.cc
index 1b2ac43..e7730e5 100644
--- a/src/jdwp/jdwp_handler.cc
+++ b/src/jdwp/jdwp_handler.cc
@@ -198,7 +198,7 @@
   VLOG(jdwp) << "  Req for class by signature '" << classDescriptor << "'";
 
   std::vector<RefTypeId> ids;
-  Dbg::FindLoadedClassBySignature(classDescriptor, ids);
+  Dbg::FindLoadedClassBySignature(classDescriptor.c_str(), ids);
 
   expandBufAdd4BE(pReply, ids.size());