IWYU: 'core' target, files starting A-C.

TBR=reed@google.com
Verbal lgtm, does not change API.

Committed: https://skia.googlesource.com/skia/+/7403d87db8e43d4c2b5b25ac22a0ebc22bd09d69

Review URL: https://codereview.chromium.org/1265033002
diff --git a/gm/shadows.cpp b/gm/shadows.cpp
index 729104c..82b5fd9 100644
--- a/gm/shadows.cpp
+++ b/gm/shadows.cpp
@@ -1,13 +1,14 @@
-
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
+
 #include "gm.h"
-#include "SkBlurMask.h"
 #include "SkBlurDrawLooper.h"
+#include "SkBlurMask.h"
+#include "SkPath.h"
 
 namespace skiagm {