cc: Glue LTHI and Scheduler changes for checker-imaging.

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index c0425180ad777b2a0bfe41e6dda4852e1f7b20a1..60f5088e4123a6c6e37cb362c00ff569c1e13127 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -93,6 +93,7 @@ LayerTreeHost::CreateSingleThreaded(
 
 LayerTreeHost::LayerTreeHost(InitParams* params, CompositorMode mode)
     : micro_benchmark_controller_(this),
+      image_worker_task_runner_(params->image_worker_task_runner),
       compositor_mode_(mode),
       ui_resource_manager_(base::MakeUnique<UIResourceManager>()),
       client_(params->client),
@@ -102,9 +103,11 @@ LayerTreeHost::LayerTreeHost(InitParams* params, CompositorMode mode)
       id_(s_layer_tree_host_sequence_number.GetNext() + 1),
       task_graph_runner_(params->task_graph_runner),
       event_listener_properties_(),
-      mutator_host_(params->mutator_host),
-      image_worker_task_runner_(params->image_worker_task_runner) {
+      mutator_host_(params->mutator_host) {
   DCHECK(task_graph_runner_);
+  DCHECK(!settings_.enable_checker_imaging || image_worker_task_runner_);
+  DCHECK(!settings_.enable_checker_imaging ||
+         settings_.image_decode_tasks_enabled);
 
   mutator_host_->SetMutatorHostClient(this);