Add a Content API around BrowserChildProcessHost, similar to what was done with ChildProcessHost....

content/public/common/child_process_host.h

Index: content/public/common/child_process_host.h
===================================================================
--- content/public/common/child_process_host.h	(revision 118420)
+++ content/public/common/child_process_host.h	(working copy)
@@ -16,7 +16,9 @@
 
 class ChildProcessHostDelegate;
 
-// Interface that all users of ChildProcessHost need to provide.
+// This represents a non-browser process. This can include traditional child
+// processes like plugins, or an embedder could even use this for long lived
+// processes that run independent of the browser process.
 class CONTENT_EXPORT ChildProcessHost : public IPC::Message::Sender {
  public:
   virtual ~ChildProcessHost() {}