Fixed tests not having MallocHooks initialized for tests in release mode.

runtime/vm/malloc_hooks.h

Index: runtime/vm/malloc_hooks.h
diff --git a/runtime/vm/malloc_hooks.h b/runtime/vm/malloc_hooks.h
index 78132c756e13f9d9f04cd91e9aed0f64ca3eee09..64e423dfed9688ec2e0335815c25d371199bca11 100644
--- a/runtime/vm/malloc_hooks.h
+++ b/runtime/vm/malloc_hooks.h
@@ -11,14 +11,19 @@
 namespace dart {
 
 class JSONObject;
+class Sample;
 
 class MallocHooks : public AllStatic {
  public:
   static void InitOnce();
   static void TearDown();
+  static bool ProfilingEnabled();
+  static bool stack_trace_collection_enabled();
+  static void set_stack_trace_collection_enabled(bool enabled);
   static void ResetStats();
   static bool Active();
   static void PrintToJSONObject(JSONObject* jsobj);
+  static Sample* GetSample(const void* ptr);
 
   static intptr_t allocation_count();
   static intptr_t heap_allocated_memory_in_bytes();