Refactor GL bindings so there is no global GLApi or DriverGL.

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 4829 matching lines @@
   // ShaderTranslatorCache.
   fragment_translator_ = NULL;
   vertex_translator_ = NULL;
 
   // Destroy the GPU Tracer which may own some in process GPU Timings.
   if (gpu_tracer_) {
     gpu_tracer_->Destroy(have_context);
     gpu_tracer_.reset();
   }
 
+  // Destroy the surface before the context, some surface destructors make GL
+  // calls.
+  surface_ = nullptr;

[jbauman, 2017/01/18 21:32:09]

This puts it in a pretty weird state where the underlying gl surface exists, but
only because it's bound to the context, so if we switch contexts after this
everything will break. Do you know which surfaces would cause this problem?

[Geoff Lang, 2017/01/19 15:40:06]

I did some investigating and it looks like the context doesn't hold any
references to the surface, they would both destruct separately.  The issue I was
dealing with was that both GLContextCGL and GLImageIOSurface make GL calls in
their destructors and if the context is destroyed before the surface then it
hits the NoContextGLApi.

+
   if (group_.get()) {
     group_->Destroy(this, have_context);
     group_ = NULL;
   }
 
   if (context_.get()) {
     context_->ReleaseCurrent(NULL);
     context_ = NULL;
   }
 }
@@ skipping 14273 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