Revert of Discard compositor frames from unloaded web content

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 942d593868124b3593d8cd735d965cd939c8f069..4ad7918622b191898a79b32db5be3317e764f434 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -104,7 +104,6 @@
       debug_state_(settings_.initial_debug_state),
       id_(s_layer_tree_host_sequence_number.GetNext() + 1),
       task_graph_runner_(params->task_graph_runner),
-      content_source_id_(0),
       event_listener_properties_(),
       mutator_host_(params->mutator_host) {
   DCHECK(task_graph_runner_);
@@ -973,13 +972,6 @@
       this, [](Layer* layer) { layer->SetNeedsDisplay(); });
 }
 
-void LayerTreeHost::SetContentSourceId(uint32_t id) {
-  if (content_source_id_ == id)
-    return;
-  content_source_id_ = id;
-  SetNeedsCommit();
-}
-
 void LayerTreeHost::RegisterLayer(Layer* layer) {
   DCHECK(!LayerById(layer->id()));
   DCHECK(!in_paint_layer_contents_);
@@ -1150,8 +1142,6 @@
 
   tree_impl->SetDeviceColorSpace(device_color_space_);
 
-  tree_impl->set_content_source_id(content_source_id_);
-
   if (pending_page_scale_animation_) {
     tree_impl->SetPendingPageScaleAnimation(
         std::move(pending_page_scale_animation_));