cc: Fix regression in TileManager InsertNodeForDecodeTask().

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 b6daab4ccfeac4a8a627aa6973ee84438ee20dc7..4dd75959d123857bfab625b520c9c6bbf1da10be 100644
--- a/cc/tiles/gpu_image_decode_controller.cc
+++ b/cc/tiles/gpu_image_decode_controller.cc
@@ -110,7 +110,11 @@ class ImageUploadTaskImpl : public TileTask {
         image_ref_(skia::SharePtr(draw_image.image())),
         source_prepare_tiles_id_(source_prepare_tiles_id) {
     DCHECK(!SkipImage(draw_image));
-    dependencies_.push_back(std::move(decode_dependency));
+    // For already-uploaded image, ImageDecodeTaskImpl is not created. The
+    // ImageUploadTaskImpl should hold valid decode dependency in
+    // |dependencies_|.
+    if (decode_dependency.get())
+      dependencies_.push_back(std::move(decode_dependency));
   }
 
   // Override from Task: