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/include/core/SkColor.h b/include/core/SkColor.h
index 4c1f9ff..1ba1331 100644
--- a/include/core/SkColor.h
+++ b/include/core/SkColor.h
@@ -1,4 +1,3 @@
-
 /*
  * Copyright 2006 The Android Open Source Project
  *
@@ -6,11 +5,11 @@
  * found in the LICENSE file.
  */
 
-
 #ifndef SkColor_DEFINED
 #define SkColor_DEFINED
 
 #include "SkScalar.h"
+#include "SkTypes.h"
 
 /** \file SkColor.h