base: Add NOTREACHED() for when using a non-supported discardable memory type.

base/memory/discardable_memory_mac.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/discardable_memory.h"
 
 #include <mach/mach.h>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ skipping 157 matching lines @@
     DISCARDABLE_MEMORY_TYPE_EMULATED,
     DISCARDABLE_MEMORY_TYPE_MALLOC
   };
   types->assign(supported_types, supported_types + arraysize(supported_types));
 }
 
 // static
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
     DiscardableMemoryType type, size_t size) {
   switch (type) {
-    case DISCARDABLE_MEMORY_TYPE_NONE:
-    case DISCARDABLE_MEMORY_TYPE_ASHMEM:
-      return scoped_ptr<DiscardableMemory>();
     case DISCARDABLE_MEMORY_TYPE_MAC: {
       scoped_ptr<DiscardableMemoryMac> memory(new DiscardableMemoryMac(size));
       if (!memory->Initialize())
         return scoped_ptr<DiscardableMemory>();
 
       return memory.PassAs<DiscardableMemory>();
     }
     case DISCARDABLE_MEMORY_TYPE_EMULATED: {
       scoped_ptr<internal::DiscardableMemoryEmulated> memory(
           new internal::DiscardableMemoryEmulated(size));
       if (!memory->Initialize())
         return scoped_ptr<DiscardableMemory>();
 
       return memory.PassAs<DiscardableMemory>();
     }
     case DISCARDABLE_MEMORY_TYPE_MALLOC: {
       scoped_ptr<internal::DiscardableMemoryMalloc> memory(
           new internal::DiscardableMemoryMalloc(size));
       if (!memory->Initialize())
         return scoped_ptr<DiscardableMemory>();
 
       return memory.PassAs<DiscardableMemory>();
     }
+    case DISCARDABLE_MEMORY_TYPE_NONE:
+    case DISCARDABLE_MEMORY_TYPE_ASHMEM:
+      NOTREACHED();
+      return scoped_ptr<DiscardableMemory>();
   }
 
   NOTREACHED();
   return scoped_ptr<DiscardableMemory>();
 }
 
 // static
 void DiscardableMemory::PurgeForTesting() {
   int state = 0;
   vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
   internal::DiscardableMemoryEmulated::PurgeForTesting();
 }
 
 }  // namespace base