Limit lifetime of GrDrawContext objects

gm/texdata.cpp

Index: gm/texdata.cpp
diff --git a/gm/texdata.cpp b/gm/texdata.cpp
index 13a1c2a6c2275e56e91386e748956cd161f94bc5..1a807c7b9bd5a57d171af1fcd9989ff3bb2b1a45 100644
--- a/gm/texdata.cpp
+++ b/gm/texdata.cpp
@@ -39,7 +39,7 @@ protected:
     void onDraw(SkCanvas* canvas) override {
         GrRenderTarget* target = canvas->internal_private_accessTopLayerRenderTarget();
         GrContext* ctx = canvas->getGrContext();
-        GrDrawContext* drawContext = ctx ? ctx->drawContext() : nullptr;
+        SkAutoTUnref<GrDrawContext> drawContext(ctx ? ctx->drawContext() : nullptr);
         if (drawContext && target) {
             SkAutoTArray<SkPMColor> gTextureData((2 * S) * (2 * S));
             static const int stride = 2 * S;