8035735: Metaspace::contains become extremely slow in some cases

Summary: Call is_metadata instead which does less work for the call in debugInfo.hpp which is called for all compiled code stack frames.
Reviewed-by: jmasa, dcubed

src/share/vm/code/debugInfo.hpp

 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -273,8 +273,8 @@ class DebugInfoReadStream : public CompressedReadStream {
   }
   Method* read_method() {
     Method* o = (Method*)(code()->metadata_at(read_int()));
-    assert(o == NULL ||
-           o->is_metaspace_object(), "meta data only");
+    // is_metadata() is a faster check than is_metaspace_object()
+    assert(o == NULL || o->is_metadata(), "meta data only");
     return o;
   }
   ScopeValue* read_object_value();

src/share/vm/oops/metadata.hpp

@@ -42,6 +42,7 @@ class Metadata : public MetaspaceObj {
   // Rehashing support for tables containing pointers to this
   unsigned int new_hash(juint seed)   { ShouldNotReachHere();  return 0; }
 
+  virtual bool is_metadata()           const volatile { return true; }
   virtual bool is_klass()              const volatile { return false; }
   virtual bool is_method()             const volatile { return false; }
   virtual bool is_methodData()         const volatile { return false; }