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

base/memory/discardable_memory_android.cc

Index: base/memory/discardable_memory_android.cc
diff --git a/base/memory/discardable_memory_android.cc b/base/memory/discardable_memory_android.cc
index acf29ac85f11eb19df32b638048d4ded8e9990a5..9e589e2f4003520c1d9afcefbbd3c5e1130c945c 100644
--- a/base/memory/discardable_memory_android.cc
+++ b/base/memory/discardable_memory_android.cc
@@ -63,9 +63,6 @@ void DiscardableMemory::GetSupportedTypes(
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
     DiscardableMemoryType type, size_t size) {
   switch (type) {
-    case DISCARDABLE_MEMORY_TYPE_NONE:
-    case DISCARDABLE_MEMORY_TYPE_MAC:
-      return scoped_ptr<DiscardableMemory>();
     case DISCARDABLE_MEMORY_TYPE_ASHMEM: {
       SharedState* const shared_state = g_shared_state.Pointer();
       scoped_ptr<internal::DiscardableMemoryAshmem> memory(
@@ -92,6 +89,10 @@ scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
 
       return memory.PassAs<DiscardableMemory>();
     }
+    case DISCARDABLE_MEMORY_TYPE_NONE:
+    case DISCARDABLE_MEMORY_TYPE_MAC:
+      NOTREACHED();
+      return scoped_ptr<DiscardableMemory>();
   }
 
   NOTREACHED();