Fixed issue where MallocHooks tests would try and re-initialize the hooks and ended up hitting an a…

runtime/vm/malloc_hooks.cc

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 #include "platform/globals.h"
 
 #if defined(DART_USE_TCMALLOC) && !defined(PRODUCT) &&                         \
     !defined(TARGET_ARCH_DBC) && !defined(TARGET_OS_FUCHSIA)
 
 #include "vm/malloc_hooks.h"
@@ skipping 245 matching lines @@
   ASSERT(malloc_hook_mutex()->IsOwnedByCurrentThread());
   active_ = false;
   original_pid_ = kInvalidPid;
   ResetStats();
   delete address_map_;
   address_map_ = NULL;
 }
 
 
 void MallocHooks::InitOnce() {
-  if (!FLAG_enable_malloc_hooks) {
+  if (!FLAG_enable_malloc_hooks || MallocHooks::Active()) {
     return;
   }
   MallocLocker ml(MallocHooksState::malloc_hook_mutex(),
                   MallocHooksState::malloc_hook_mutex_owner());
   ASSERT(!MallocHooksState::Active());
 
   MallocHooksState::Init();
 
   // Register malloc hooks.
   bool success = false;
   success = MallocHook::AddNewHook(&MallocHooksState::RecordAllocHook);
   ASSERT(success);
   success = MallocHook::AddDeleteHook(&MallocHooksState::RecordFreeHook);
   ASSERT(success);
 }
 
 
 void MallocHooks::TearDown() {
-  if (!FLAG_enable_malloc_hooks) {
+  if (!FLAG_enable_malloc_hooks || !MallocHooks::Active()) {
     return;
   }
   MallocLocker ml(MallocHooksState::malloc_hook_mutex(),
                   MallocHooksState::malloc_hook_mutex_owner());
   ASSERT(MallocHooksState::Active());
 
   // Remove malloc hooks.
   bool success = false;
   success = MallocHook::RemoveNewHook(&MallocHooksState::RecordAllocHook);
   ASSERT(success);
@@ skipping 142 matching lines @@
       MallocHooksState::address_map()->Remove(ptr);
       delete allocation_info;
     }
   }
 }
 
 }  // namespace dart
 
 #endif  // defined(DART_USE_TCMALLOC) && !defined(PRODUCT) &&
         // !defined(TARGET_ARCH_DBC) && !defined(TARGET_OS_FUCHSIA)