gpu: fix gpu process crashed on win_blink_rel due to dcheck in CopyTextureCHROMIUM.

gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.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_copy_texture_chromium.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "gpu/command_buffer/service/gl_utils.h"
@@ skipping 242 matching lines @@
 namespace gpu {
 
 CopyTextureCHROMIUMResourceManager::CopyTextureCHROMIUMResourceManager()
     : initialized_(false),
       vertex_shaders_(NUM_VERTEX_SHADERS, 0u),
       fragment_shaders_(NUM_FRAGMENT_SHADERS, 0u),
       buffer_id_(0u),
       framebuffer_(0u) {}
 
 CopyTextureCHROMIUMResourceManager::~CopyTextureCHROMIUMResourceManager() {
-  DCHECK(!buffer_id_);
-  DCHECK(!framebuffer_);
+  // |buffer_id_| and |framebuffer_| can be not-null because when GPU context is
+  // lost, this class can be deleted without releasing resources like
+  // GLES2DecoderImpl.

[piman, 2014/12/05 20:34:12]

nit: is there a way to check that the GL resources were cleared if the context
was not lost? I wouldn't want a new field introduced that we forgot to clear and
cause a leak. Since we don't track GL-level objects, it can be very hard to
detect and track down this kind of leak.

 }
 
 void CopyTextureCHROMIUMResourceManager::Initialize(
     const gles2::GLES2Decoder* decoder) {
   COMPILE_ASSERT(
       kVertexPositionAttrib == 0u,
       Position_attribs_must_be_0);
   DCHECK(!buffer_id_);
   DCHECK(!framebuffer_);
   DCHECK(programs_.empty());
@@ skipping 198 matching lines @@
   decoder->RestoreTextureState(dest_id);
   decoder->RestoreTextureUnitBindings(0);
   decoder->RestoreActiveTexture();
   decoder->RestoreProgramBindings();
   decoder->RestoreBufferBindings();
   decoder->RestoreFramebufferBindings();
   decoder->RestoreGlobalState();
 }
 
 }  // namespace gpu