cc: Unittest for checking already failed image decode task.

cc/tiles/gpu_image_decode_controller.cc

Index: cc/tiles/gpu_image_decode_controller.cc
diff --git a/cc/tiles/gpu_image_decode_controller.cc b/cc/tiles/gpu_image_decode_controller.cc
index 17f66d543d3f43d46bc97d7f06a6e3e2a7e9eb7e..b7dbd55f116d1900fca133a64d710abf086376a3 100644
--- a/cc/tiles/gpu_image_decode_controller.cc
+++ b/cc/tiles/gpu_image_decode_controller.cc
@@ -821,4 +821,13 @@ SkImageInfo GpuImageDecodeController::CreateImageInfoForDrawImage(
       ResourceFormatToClosestSkColorType(format_), kPremul_SkAlphaType);
 }
 
+void GpuImageDecodeController::SetImageDecodingFailedForTesting(
+    const DrawImage& image) {
+  base::AutoLock lock(lock_);
+  auto found = image_data_.Peek(image.image()->uniqueID());
+  DCHECK(found != image_data_.end());
+  ImageData* image_data = found->second.get();
+  image_data->decode.decode_failure = true;
+}
+
 }  // namespace cc