cc/blimp: Remove the LayerTreeSettings serialization.

cc/proto/compositor_message_to_impl.proto

Index: cc/proto/compositor_message_to_impl.proto
diff --git a/cc/proto/compositor_message_to_impl.proto b/cc/proto/compositor_message_to_impl.proto
index 7b15ff11ece6ec4f803befd4ade8e08780a2ce47..4c8a1e1a18dfd03c1f7da5301190ef6f116ab136 100644
--- a/cc/proto/compositor_message_to_impl.proto
+++ b/cc/proto/compositor_message_to_impl.proto
@@ -8,7 +8,6 @@ option optimize_for = LITE_RUNTIME;
 
 import "commit_earlyout_reason.proto";
 import "layer_tree_host.proto";
-import "layer_tree_settings.proto";
 import "rect.proto";
 
 package cc.proto;
@@ -90,9 +89,6 @@ message CompositorMessageToImpl {
 
   // Only one of the following fields will be set per CompositorMessageToImpl.
 
-  // Set for message Type::INITIALIZE_IMPL.
-  optional InitializeImpl initialize_impl_message = 2;
-
   // Set for message Type::SET_DEFER_COMMITS.
   optional SetDeferCommits defer_commits_message = 3;
 
@@ -106,13 +102,6 @@ message CompositorMessageToImpl {
   optional SetNeedsRedraw set_needs_redraw_message = 6;
 }
 
-// The embedder of the remote client compositor should process the
-// InitializeImpl message to retrieve the LayerTreeSettings sent from the
-// server. The settings sent from the server may be modified by the embedder.
-message InitializeImpl {
-  optional LayerTreeSettings layer_tree_settings = 1;
-}
-
 message SetDeferCommits {
   // If set to true, the client will defer sending any BEGIN_MAIN_FRAME messages
   // to start a commit. The server must send a message with defer_commits set to