Cloning a bunch of stuff from the native_client repository at r6528

ppapi/native_client/src/shared/ppapi_proxy/browser_upcall.h

Index: ppapi/native_client/src/shared/ppapi_proxy/browser_upcall.h
===================================================================
--- ppapi/native_client/src/shared/ppapi_proxy/browser_upcall.h	(revision 0)
+++ ppapi/native_client/src/shared/ppapi_proxy/browser_upcall.h	(revision 0)
@@ -0,0 +1,42 @@
+// Copyright (c) 2010 The Native Client Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
+//
+// This is an early draft of background thread support.
+// Until it is complete, we assume that all functions proxy functions
+// (but CallOnMainThread) are called on the main thread.
+//
+// WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
+//
+// Support for "upcalls" -- RPCs to the browser that are done from other than
+// the PPAPI main thread.  These calls are synchronized by the ppapi_proxy
+// library at the plugin end.
+
+#include "native_client/src/include/portability.h"
+
+struct NaClSrpcChannel;
+struct NaClThread;
+
+namespace nacl {
+class DescWrapper;
+}  // namespace nacl
+
+namespace ppapi_proxy {
+
+class BrowserUpcall {
+ public:
+  // If successful, creates the listener thread in the browser that will handle
+  // upcalls and returns the plugin end of the upcall channel.  The caller
+  // takes ownership of this descriptor.  If either thread or socket creation
+  // fails, this method returns NULL.
+  // The thread's state is maintained by nacl_thread.  Upcall processing may
+  // cause rpcs to be performed on main_channel (e.g., CallOnMainThread),
+  // so the interface takes main_channel, but the upcall thread does not have
+  // ownership.
+  static nacl::DescWrapper* Start(NaClThread* nacl_thread,
+                                  NaClSrpcChannel* main_channel);
+};
+
+}  // namespace ppapi_proxy