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/convexpolyclip.cpp b/gm/convexpolyclip.cpp
index 0478b51..2ed17f2 100644
--- a/gm/convexpolyclip.cpp
+++ b/gm/convexpolyclip.cpp
@@ -10,6 +10,7 @@
 
 #include "SkBitmap.h"
 #include "SkGradientShader.h"
+#include "SkPath.h"
 #include "SkTLList.h"
 
 static SkBitmap make_bmp(int w, int h) {