gpu: Add GpuFence framework.

ui/gl/gl_fence.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gl/gl_fence.h"
 
 #include "base/compiler_specific.h"
 #include "build/build_config.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
@@ skipping 65 matching lines @@
 }
 
 void GLFence::ResetState() {
   NOTIMPLEMENTED();
 }
 
 void GLFence::Invalidate() {
   NOTIMPLEMENTED();
 }
 
+bool GLFence::SignalSupported() {
+  // Signaling a fence isn't supported by default.
+  return false;
+}
+
+void GLFence::Signal() {
+  NOTIMPLEMENTED();
+}
+
 }  // namespace gl