IWYU for tests starting with 'D'.

Change-Id: I9189e4b56ce1635b627119733447c2ed4220753d
Reviewed-on: https://skia-review.googlesource.com/129319
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/tests/DiscardableMemoryPoolTest.cpp b/tests/DiscardableMemoryPoolTest.cpp
index c91e827..6ea0e9b 100644
--- a/tests/DiscardableMemoryPoolTest.cpp
+++ b/tests/DiscardableMemoryPoolTest.cpp
@@ -4,10 +4,14 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
-#include "SkDiscardableMemoryPool.h"
 
+#include "SkDiscardableMemory.h"
+#include "SkDiscardableMemoryPool.h"
+#include "SkRefCnt.h"
 #include "Test.h"
 
+#include <memory>
+
 DEF_TEST(DiscardableMemoryPool, reporter) {
     sk_sp<SkDiscardableMemoryPool> pool(SkDiscardableMemoryPool::Make(1));
     pool->setRAMBudget(3);