Limit lifetime of GrDrawContext objects

src/image/SkImage_Gpu.cpp

Index: src/image/SkImage_Gpu.cpp
diff --git a/src/image/SkImage_Gpu.cpp b/src/image/SkImage_Gpu.cpp
index 6655e39c17d400963708767639e3981df22b1fc0..fdcb87136db528f79b666ff8e39ac0ee6dbcba9a 100644
--- a/src/image/SkImage_Gpu.cpp
+++ b/src/image/SkImage_Gpu.cpp
@@ -254,7 +254,11 @@ SkImage* SkImage::NewFromYUVTexturesCopy(GrContext* ctx , SkYUVColorSpace colorS
 
     const SkRect rect = SkRect::MakeWH(SkIntToScalar(dstDesc.fWidth),
                                        SkIntToScalar(dstDesc.fHeight));
-    GrDrawContext* drawContext = ctx->drawContext();
+    SkAutoTUnref<GrDrawContext> drawContext(ctx->drawContext());
+    if (!drawContext) {
+        return nullptr;
+    }
+
     drawContext->drawRect(dst->asRenderTarget(), GrClip::WideOpen(), paint, SkMatrix::I(), rect);
     ctx->flushSurfaceWrites(dst);
     return new SkImage_Gpu(dstDesc.fWidth, dstDesc.fHeight, kNeedNewImageUniqueID,