Add a useful DCHECK to RestoreCurrentTextureBindings.

gpu/command_buffer/service/gles2_cmd_decoder.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 "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 2278 matching lines @@
     : function_name_(function_name),
       error_state_(error_state) {
   ERRORSTATE_COPY_REAL_GL_ERRORS_TO_WRAPPER(error_state_, function_name_);
 }
 
 ScopedGLErrorSuppressor::~ScopedGLErrorSuppressor() {
   ERRORSTATE_CLEAR_REAL_GL_ERRORS(error_state_, function_name_);
 }
 
 static void RestoreCurrentTextureBindings(ContextState* state, GLenum target) {
+  DCHECK(!state->texture_units.empty());
   TextureUnit& info = state->texture_units[0];
   GLuint last_id;
   scoped_refptr<TextureRef>& texture_ref = info.GetInfoForTarget(target);
   if (texture_ref.get()) {
     last_id = texture_ref->service_id();
   } else {
     last_id = 0;
   }
 
   glBindTexture(target, last_id);
@@ skipping 14738 matching lines @@
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu