content/blimp: Set up hooks for enabling LTHRemote in the renderer.

cc/layers/picture_layer.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/picture_layer.h"
 
 #include "base/auto_reset.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/blimp/client_picture_cache.h"
 #include "cc/blimp/engine_picture_cache.h"
@@ skipping 190 matching lines @@
 bool PictureLayer::HasDrawableContent() const {
   return picture_layer_inputs_.client && Layer::HasDrawableContent();
 }
 
 void PictureLayer::SetTypeForProtoSerialization(proto::LayerNode* proto) const {
   proto->set_type(proto::LayerNode::PICTURE_LAYER);
 }
 
 void PictureLayer::LayerSpecificPropertiesToProto(proto::LayerProperties* proto,
                                                   bool inputs_only) {
+  DCHECK(GetLayerTree());
+  DCHECK(GetLayerTree()->engine_picture_cache());

[Wez, 2016/10/13 16:53:52]

nit: Is it worth DCHECK()ing these, given that you're going to de-reference
them, and thereby crash, later in this function?

[Khushal, 2016/10/13 18:47:28]

I found an unhelpful seg-fault instead of a pretty stack trace when I was
debugging this, so that's why decided to add it here.

+
   Layer::LayerSpecificPropertiesToProto(proto, inputs_only);
   DropRecordingSourceContentIfInvalid();
   proto::PictureLayerProperties* picture = proto->mutable_picture();
 
   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) {
     picture_layer_inputs_.display_list->ToProtobuf(
         picture->mutable_display_list());
@@ skipping 90 matching lines @@
     picture_layer_inputs_.display_list = nullptr;
     picture_layer_inputs_.painter_reported_memory_usage = 0;
   }
 }
 
 const DisplayItemList* PictureLayer::GetDisplayItemList() {
   return picture_layer_inputs_.display_list.get();
 }
 
 }  // namespace cc