Add BlimpDocument, pull out functions in BlimpCompositor.

blimp/client/core/compositor/blimp_compositor.cc

Index: blimp/client/core/compositor/blimp_compositor.cc
diff --git a/blimp/client/core/compositor/blimp_compositor.cc b/blimp/client/core/compositor/blimp_compositor.cc
index b38bb723e0eeb0a534fc2631a8b0cf3af0987f93..b1f2ab8530cf9bba24f23758eb72afcac2664711 100644
--- a/blimp/client/core/compositor/blimp_compositor.cc
+++ b/blimp/client/core/compositor/blimp_compositor.cc
@@ -58,11 +58,9 @@ void RequireCallback(cc::SurfaceManager* manager,
 }  // namespace
 
 BlimpCompositor::BlimpCompositor(
-    int render_widget_id,
     BlimpCompositorDependencies* compositor_dependencies,
     BlimpCompositorClient* client)
-    : render_widget_id_(render_widget_id),
-      client_(client),
+    : client_(client),
       compositor_dependencies_(compositor_dependencies),
       proxy_client_(nullptr),
       compositor_frame_sink_request_pending_(false),
@@ -141,7 +139,7 @@ void BlimpCompositor::SetProtoReceiver(ProtoReceiver* receiver) {
 
 void BlimpCompositor::SendCompositorProto(
     const cc::proto::CompositorMessage& proto) {
-  client_->SendCompositorMessage(render_widget_id_, proto);
+  client_->SendCompositorMessage(proto);
 }
 
 void BlimpCompositor::OnCompositorMessageReceived(
@@ -201,7 +199,7 @@ void BlimpCompositor::OnContextProvidersCreated(
 
 void BlimpCompositor::SendWebGestureEvent(
     const blink::WebGestureEvent& gesture_event) {
-  client_->SendWebGestureEvent(render_widget_id_, gesture_event);
+  client_->SendWebGestureEvent(gesture_event);
 }
 
 void BlimpCompositor::BindToProxyClient(
@@ -283,7 +281,7 @@ void BlimpCompositor::DestroyDelegatedContent() {
 
 void BlimpCompositor::CreateLayerTreeHost() {
   DCHECK(!host_);
-  VLOG(1) << "Creating LayerTreeHost for render widget: " << render_widget_id_;
+  VLOG(1) << "Creating LayerTreeHost.";
 
   // Create the LayerTreeHost
   cc::LayerTreeHostInProcess::InitParams params;
@@ -318,8 +316,8 @@ void BlimpCompositor::CreateLayerTreeHost() {
 
 void BlimpCompositor::DestroyLayerTreeHost() {
   DCHECK(host_);
-  VLOG(1) << "Destroying LayerTreeHost for render widget: "
-          << render_widget_id_;
+  VLOG(1) << "Destroying LayerTreeHost.";
+
   // Tear down the output surface connection with the old LayerTreeHost
   // instance.
   DestroyDelegatedContent();