Get rid of view_messages.h includes in chrome\renderer.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
===================================================================
--- content/renderer/render_thread_impl.cc	(revision 105613)
+++ content/renderer/render_thread_impl.cc	(working copy)
@@ -365,6 +365,12 @@
   return ChildThread::RemoveRoute(routing_id);
 }
 
+int RenderThreadImpl::GenerateRoutingID() {
+  int routing_id = MSG_ROUTING_NONE;
+  Send(new ViewHostMsg_GenerateRoutingID(&routing_id));
+  return routing_id;
+}
+
 void RenderThreadImpl::AddFilter(IPC::ChannelProxy::MessageFilter* filter) {
   channel()->AddFilter(filter);
 }