cc: Add image decode queue functionality to image manager.

cc/test/layer_tree_test.cc

Index: cc/test/layer_tree_test.cc
diff --git a/cc/test/layer_tree_test.cc b/cc/test/layer_tree_test.cc
index 740880a2d5f18c9d42083a34cee7e36988225fe1..dac3cbb773a39cdbf0e4dde7cf4aaaef2dd1c227 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -117,7 +117,8 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
                           stats_instrumentation,
                           task_graph_runner,
                           AnimationHost::CreateForTesting(ThreadInstance::IMPL),
-                          0),
+                          0,
+                          nullptr),
         test_hooks_(test_hooks),
         block_notify_ready_to_activate_for_testing_(false),
         notify_ready_to_activate_was_blocked_(false) {}
@@ -351,6 +352,7 @@ class LayerTreeHostForTesting : public LayerTreeHostInProcess {
     params.task_graph_runner = task_graph_runner;
     params.settings = &settings;
     params.mutator_host = mutator_host;
+    params.image_worker_task_runner = nullptr;
 
     std::unique_ptr<LayerTreeHostForTesting> layer_tree_host(
         new LayerTreeHostForTesting(test_hooks, &params, mode));