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/SurfaceTest.cpp b/tests/SurfaceTest.cpp
index dd71943..b85ac81 100644
--- a/tests/SurfaceTest.cpp
+++ b/tests/SurfaceTest.cpp
@@ -13,6 +13,7 @@
 #include "SkImage_Base.h"
 #include "SkOverdrawCanvas.h"
 #include "SkPath.h"
+#include "SkRegion.h"
 #include "SkRRect.h"
 #include "SkSurface.h"
 #include "SkUtils.h"