Update Context Client Visibility to use Scoped Pattern

gpu/command_buffer/client/scoped_visibility_impl.cc

+// Copyright 2016 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 "gpu/command_buffer/client/scoped_visibility_impl.h"
+
+#include "base/logging.h"
+
+namespace gpu {
+
+ScopedVisibilityImpl::ScopedVisibilityImpl(ContextSupport* context_support)
+    : initial_context_support_(context_support), released_(false) {}
+
+ScopedVisibilityImpl::~ScopedVisibilityImpl() {
+  DCHECK(released_);
+}
+
+void ScopedVisibilityImpl::Release(ContextSupport* context_support) {
+  DCHECK(!released_);
+  DCHECK_EQ(initial_context_support_, context_support);
+  released_ = true;
+}
+
+}  // namespace gpu