add gm for clipRegion

BUG=skia:

Change-Id: Ie69db51b6fac193373fd57225370d0081295facb
Reviewed-on: https://skia-review.googlesource.com/8394
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/gm/clipdrawdraw.cpp b/gm/clipdrawdraw.cpp
index 1aecb9f..389d7e3 100644
--- a/gm/clipdrawdraw.cpp
+++ b/gm/clipdrawdraw.cpp
@@ -47,3 +47,20 @@
         Draw(canvas, rect1);
         Draw(canvas, rect2);
 }
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+DEF_SIMPLE_GM(clip_region, canvas, 256, 256) {
+    SkRegion rgn({ 10, 10, 100, 100 });
+
+    canvas->save();
+    canvas->clipRegion(rgn);
+    canvas->drawColor(SK_ColorRED);
+    canvas->restore();
+
+    SkRect bounds = { 30, 30, 80, 80 };
+    canvas->saveLayer(&bounds, nullptr);
+    canvas->clipRegion(rgn);
+    canvas->drawColor(SK_ColorBLUE);
+    canvas->restore();
+}