Add initial GpuMemoryBufferSurfaceTexture implementation.

ui/gl/android/surface_texture_tracker.cc

+// Copyright 2014 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/android/surface_texture_tracker.h"
+
+#include "base/logging.h"
+
+namespace gfx {
+namespace {
+SurfaceTextureTracker* g_instance = NULL;
+}  // namespace
+
+// static
+SurfaceTextureTracker* SurfaceTextureTracker::GetInstance() {
+  DCHECK(g_instance);
+  return g_instance;
+}
+
+// static
+void SurfaceTextureTracker::InitInstance(SurfaceTextureTracker* tracker) {
+  DCHECK(!g_instance);
+  g_instance = tracker;
+}
+
+}  // namespace gfx