Add runtime flag to turn compressed alpha masks on

tools/render_pictures_main.cpp

Index: tools/render_pictures_main.cpp
diff --git a/tools/render_pictures_main.cpp b/tools/render_pictures_main.cpp
index 23d973f901092989b2a6c0f64f92d23e7e33a395..31625b49a0b6378cf9d4bee8f9152b6238718031 100644
--- a/tools/render_pictures_main.cpp
+++ b/tools/render_pictures_main.cpp
@@ -292,7 +292,12 @@ static bool render_picture(const SkString& inputPath, const SkString* writePath,
             referenceRenderer->ref();  // to match auto unref below
             arbbh.set(referenceRenderer, sk_tools::PictureRenderer::kNone_BBoxHierarchyType);
         } else {
+#if SK_SUPPORT_GPU
+            referenceRenderer = SkNEW_ARGS(sk_tools::SimplePictureRenderer,
+                                           (renderer.getGrContextOptions()));
+#else
             referenceRenderer = SkNEW(sk_tools::SimplePictureRenderer);
+#endif
         }
         SkAutoTUnref<sk_tools::PictureRenderer> aurReferenceRenderer(referenceRenderer);