GM: replace boilerplate with macros

gm/mipmap.cpp

Index: gm/mipmap.cpp
diff --git a/gm/mipmap.cpp b/gm/mipmap.cpp
index 4eb5c2aa3ca2be0c7cdc42725618011e8365cbde..b0b0cc487c8076de3188e2bca17600f734ff4e1e 100644
--- a/gm/mipmap.cpp
+++ b/gm/mipmap.cpp
@@ -28,7 +28,7 @@ static SkImage* make_image() {
     return surface->newImageSnapshot();
 }
 
-static void test_mip(SkCanvas* canvas) {
+DEF_SIMPLE_GM(mipmap, canvas, 400, 200) {
     SkAutoTUnref<SkImage> img(make_image());//SkImage::NewFromEncoded(data));
 
     SkPaint paint;
@@ -48,21 +48,3 @@ static void test_mip(SkCanvas* canvas) {
     canvas->drawImage(img, 20, 20, nullptr);
 }
 
-class MipMapGM : public skiagm::GM {
-public:
-    MipMapGM() {}
-
-protected:
-    SkString onShortName() override { return SkString("mipmap"); }
-
-    SkISize onISize() override { return SkISize::Make(400, 200); }
-
-    void onDraw(SkCanvas* canvas) override {
-        test_mip(canvas);
-    }
-
-private:
-    typedef skiagm::GM INHERITED;
-};
-DEF_GM( return new MipMapGM; )
-