IWYU for test files starting with 'A'.

While testing some changes to iwyu, started fixing some files. Made it
to AsADashTest.cpp before running into
https://github.com/include-what-you-use/include-what-you-use/issues/364

Change-Id: I42b65df4f1f8116e0ea1b2cd774651990db1b132
Reviewed-on: https://skia-review.googlesource.com/111861
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/tests/ArenaAllocTest.cpp b/tests/ArenaAllocTest.cpp
index 137e60e..e4da0b8 100644
--- a/tests/ArenaAllocTest.cpp
+++ b/tests/ArenaAllocTest.cpp
@@ -5,9 +5,14 @@
  * found in the LICENSE file.
  */
 
-#include "Test.h"
 #include "SkArenaAlloc.h"
 #include "SkRefCnt.h"
+#include "SkTypes.h"
+#include "Test.h"
+
+#include <memory>
+#include <new>
+#include <type_traits>
 
 namespace {