Add IPC messages to transfer compositor protos

blimp/engine/browser/blimp_engine_session.cc

Index: blimp/engine/browser/blimp_engine_session.cc
diff --git a/blimp/engine/browser/blimp_engine_session.cc b/blimp/engine/browser/blimp_engine_session.cc
index 47bf3301c7cffe720415ac02bc09865e350ec95d..fc1597b31476d815956d6e1b0ba288a86742275b 100644
--- a/blimp/engine/browser/blimp_engine_session.cc
+++ b/blimp/engine/browser/blimp_engine_session.cc
@@ -135,7 +135,8 @@ void BlimpEngineSession::Reload(const int target_tab_id) {
 
 net::Error BlimpEngineSession::OnBlimpMessage(const BlimpMessage& message) {
   DCHECK(message.type() == BlimpMessage::CONTROL ||
-         message.type() == BlimpMessage::NAVIGATION);
+         message.type() == BlimpMessage::NAVIGATION ||
+         message.type() == BlimpMessage::COMPOSITOR);
 
   if (message.type() == BlimpMessage::CONTROL) {
     switch (message.control().type()) {
@@ -228,6 +229,10 @@ void BlimpEngineSession::ActivateContents(content::WebContents* contents) {
   contents->GetRenderViewHost()->GetWidget()->Focus();
 }
 
+void BlimpEngineSession::HandleCompositorProto(const std::vector<char>& proto) {
+  // TODO(dtrainor): Send the compositor proto.
+}
+
 void BlimpEngineSession::PlatformSetContents(
     scoped_ptr<content::WebContents> new_contents) {
   new_contents->SetDelegate(this);