Implemented basic heap memory allocation tracking in MallocHooks using hooks registered with tcmall…

runtime/vm/malloc_hooks_unsupported.cc

Index: runtime/vm/malloc_hooks_unsupported.cc
diff --git a/runtime/vm/malloc_hooks_unsupported.cc b/runtime/vm/malloc_hooks_unsupported.cc
index 65edca7bff776d8d8c571b97c1e3e95c0e199a2c..73ce102c60beccaca349c0bba69ee49df154d5cd 100644
--- a/runtime/vm/malloc_hooks_unsupported.cc
+++ b/runtime/vm/malloc_hooks_unsupported.cc
@@ -2,14 +2,19 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#if defined(DART_USE_TCMALLOC)
+#if !defined(DART_USE_TCMALLOC)
 
 #include "vm/malloc_hooks.h"
 
 namespace dart {
 
 void MallocHooks::Init() {
-  // TODO(bkonyi): Implement
+  // Do nothing.
+}
+
+
+void MallocHooks::TearDown() {
+  // Do nothing.
 }
 
 }  // namespace dart