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

cc/blimp/layer_tree_host_remote.cc

Index: cc/blimp/layer_tree_host_remote.cc
diff --git a/cc/blimp/layer_tree_host_remote.cc b/cc/blimp/layer_tree_host_remote.cc
index df457b79f99dc27c4ca39271efa4a06c7ebc65c3..56418c88418a2725a4e77caa8a73e0f68c70bffc 100644
--- a/cc/blimp/layer_tree_host_remote.cc
+++ b/cc/blimp/layer_tree_host_remote.cc
@@ -235,8 +235,9 @@ void LayerTreeHostRemote::DidStopFlinging() {
 
 void LayerTreeHostRemote::SetDebugState(
     const LayerTreeDebugState& debug_state) {
-  // TODO(khushalsagar): Figure out if we need to send these to the client.
-  NOTREACHED();
+  // If any debugging needs to be enabled, ideally it should be using the
+  // compositor on the client directly. But the setup code will always set this
+  // on initialization, even if the settings end up being a no-op.

[Wez, 2016/10/19 22:15:28]

This comment is rather confusing.  Are you simply saying that LTHR ignores
|debug_state| since there's no actual compositing happening at the sending end -
only the remote end needs to have debug state set?

[Khushal, 2016/10/20 01:29:33]

Yes, only the remoting end should need to have this set and I'm not sure if
there is a use-case for having this plumbed to the client from the engine
through compositor messages, rather than something setting it on the client-side
directly.

I think dev-tools uses this, but I wanted to defer adding it till we know how
that is going to be setup. Wdyt? 

 }
 
 const LayerTreeDebugState& LayerTreeHostRemote::GetDebugState() const {