Revert "Revert "IWYU""

This reverts commit 3c727d2386059c1d7cbdcdc9bef5fa18ed33667e.

BUG=skia:

Change-Id: I72e9b40fec96d044e0ac12906669a52529e77882
Reviewed-on: https://skia-review.googlesource.com/8356
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/tests/PathOpsExtendedTest.cpp b/tests/PathOpsExtendedTest.cpp
index d70deb3..279faa4 100644
--- a/tests/PathOpsExtendedTest.cpp
+++ b/tests/PathOpsExtendedTest.cpp
@@ -12,6 +12,7 @@
 #include "SkMatrix.h"
 #include "SkMutex.h"
 #include "SkPaint.h"
+#include "SkRegion.h"
 #include "SkStream.h"
 
 #include <stdlib.h>