Extend more runtime envs for generateMipmap srgb emulation

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 6131 matching lines @@
       texture_zero_level_set = true;
     }
   }
 
   bool enable_srgb = 0;
   if (target == GL_TEXTURE_2D) {
     tex->GetLevelType(target, tex->base_level(), &type, &internal_format);
     enable_srgb =
         GetColorEncodingFromInternalFormat(internal_format) == GL_SRGB;
   }
-  if (!enable_srgb || !feature_info_->feature_flags().desktop_srgb_support ||
-      !workarounds().decode_encode_srgb_for_generatemipmap) {
-    if (feature_info_->feature_flags().desktop_srgb_support) {
-      state_.EnableDisableFramebufferSRGB(enable_srgb);
-    }
-    glGenerateMipmapEXT(target);
-  } else {
+  if (enable_srgb && feature_info_->feature_flags().desktop_srgb_support) {
+    state_.EnableDisableFramebufferSRGB(enable_srgb);
+  }
+  if (enable_srgb && workarounds().decode_encode_srgb_for_generatemipmap) {
     if (target == GL_TEXTURE_2D) {
-      state_.EnableDisableFramebufferSRGB(true);
       if (!InitializeSRGBConverter("generateMipmap")) {
         return;
       }
       srgb_converter_->GenerateMipmap(this, tex, target);
     } else {
       // TODO(yizhou): If the target is GL_TEXTURE_3D or GL_TEXTURE_2D_ARRAY,

[Zhenyao Mo, 2016/12/07 22:50:38]

Just noticed: what about CUBEMAP?

       // this change can not generate correct mipmap.
       glGenerateMipmapEXT(target);
     }
+  } else {
+    glGenerateMipmapEXT(target);
   }
 
   if (texture_zero_level_set) {
     // This may have some unwanted side effects, but we expect command buffer
     // validation to prevent you from doing anything weird with the texture
     // after this, like calling texSubImage2D sucessfully.
     glTexImage2D(target, 0, internal_format, 0, 0, 0, format, type, nullptr);
   }
 
   if (workarounds().set_texture_filter_before_generating_mipmap) {
@@ skipping 12751 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