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/tools/debugger/SkDrawCommand.h b/tools/debugger/SkDrawCommand.h
index 266fc99..964badc 100644
--- a/tools/debugger/SkDrawCommand.h
+++ b/tools/debugger/SkDrawCommand.h
@@ -11,6 +11,7 @@
 #include "SkCanvas.h"
 #include "SkTLazy.h"
 #include "SkPath.h"
+#include "SkRegion.h"
 #include "SkRRect.h"
 #include "SkRSXform.h"
 #include "SkString.h"