Add gl tests to make sure when a buffer is unmapped, all access path generates an INVALID_OPERATION.

gpu/command_buffer/service/transform_feedback_manager.cc

 // Copyright (c) 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/service/transform_feedback_manager.h"
 
 #include "gpu/command_buffer/service/buffer_manager.h"
 #include "ui/gl/gl_version_info.h"
 
 namespace gpu {
@@ skipping 96 matching lines @@
   auto it = transform_feedbacks_.find(client_id);
   return it != transform_feedbacks_.end() ? it->second.get() : nullptr;
 }
 
 void TransformFeedbackManager::RemoveTransformFeedback(GLuint client_id) {
   if (client_id) {
     transform_feedbacks_.erase(client_id);
   }
 }
 
-void TransformFeedbackManager::RemoveBoundBuffer(Buffer* buffer) {
-  for (auto iter = transform_feedbacks_.begin();
-       iter != transform_feedbacks_.end(); ++iter) {
-    iter->second->RemoveBoundBuffer(buffer);
-  }
-}
-
 }  // namespace gles2
 }  // namespace gpu