cc/blimp: Add (de)-serialization for PictureLayer and ScrollbarLayer.

cc/layers/picture_layer.cc

Index: cc/layers/picture_layer.cc
diff --git a/cc/layers/picture_layer.cc b/cc/layers/picture_layer.cc
index 25e6c3e679b0958eb7c59f853b7e49cb26557a01..881a8b36c3529c8c3f4fef3cd03ebfc96ee25295 100644
--- a/cc/layers/picture_layer.cc
+++ b/cc/layers/picture_layer.cc
@@ -36,6 +36,14 @@ PictureLayer::PictureLayer(ContentLayerClient* client)
   picture_layer_inputs_.client = client;
 }
 
+PictureLayer::PictureLayer(int engine_layer_id, ContentLayerClient* client)
+    : Layer(engine_layer_id),
+      instrumentation_object_tracker_(id()),
+      update_source_frame_number_(-1),
+      is_mask_(false) {
+  picture_layer_inputs_.client = client;
+}
+
 PictureLayer::PictureLayer(ContentLayerClient* client,
                            std::unique_ptr<RecordingSource> source)
     : PictureLayer(client) {
@@ -210,10 +218,9 @@ void PictureLayer::LayerSpecificPropertiesToProto(proto::LayerProperties* proto,
                                                   bool inputs_only) {
   Layer::LayerSpecificPropertiesToProto(proto, inputs_only);
   DropRecordingSourceContentIfInvalid();
-
   proto::PictureLayerProperties* picture = proto->mutable_picture();
-  recording_source_->ToProtobuf(picture->mutable_recording_source());
 
+  picture->set_nearest_neighbor(picture_layer_inputs_.nearest_neighbor);
   RectToProto(picture_layer_inputs_.recorded_viewport,
               picture->mutable_recorded_viewport());
   if (picture_layer_inputs_.display_list) {
@@ -229,12 +236,13 @@ void PictureLayer::LayerSpecificPropertiesToProto(proto::LayerProperties* proto,
     }
   }
 
+  if (inputs_only)
+    return;
+
+  recording_source_->ToProtobuf(picture->mutable_recording_source());
   RegionToProto(last_updated_invalidation_, picture->mutable_invalidation());
   picture->set_is_mask(is_mask_);
-  picture->set_nearest_neighbor(picture_layer_inputs_.nearest_neighbor);
-
   picture->set_update_source_frame_number(update_source_frame_number_);
-
   last_updated_invalidation_.Clear();
 }