Initialize depth texture using tex{Sub}Image2D except for ANGLE ES2

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 12181 matching lines @@
                                   int level,
                                   unsigned format,
                                   unsigned type,
                                   int xoffset,
                                   int yoffset,
                                   int width,
                                   int height) {
   DCHECK(target != GL_TEXTURE_3D && target != GL_TEXTURE_2D_ARRAY &&
          target != GL_TEXTURE_EXTERNAL_OES);
   uint32_t channels = GLES2Util::GetChannelsForFormat(format);
-  if ((feature_info_->feature_flags().angle_depth_texture ||
-       feature_info_->IsWebGL2OrES3Context())
-      && (channels & GLES2Util::kDepth) != 0) {
+  if ((channels & GLES2Util::kDepth) != 0 &&
+      feature_info_->feature_flags().angle_depth_texture &&
+      feature_info_->gl_version_info().is_es2) {

[Kai Ninomiya, 2016/11/17 20:41:22]

I think the logic here is valid but doesn't quite make sense. If
angle_depth_texture is false, I think neither path will work. Perhaps it should
throw an error in that case:

if ((channels & GLES2Util::kDepth) != 0 &&
    !feature_info_->feature_flags().angle_depth_texture) {
  // this is an error
}

if ((channels & GLES2Util::kDepth) != 0 &&
    feature_info_->gl_version_info().is_es2) {

[Zhenyao Mo, 2016/11/17 20:46:58]

You are right.  I can move feature_info_->feature_flags().angle_depth_texture
into the if body as a DCHECK

     // It's a depth format and ANGLE doesn't allow texImage2D or texSubImage2D
-    // on depth formats.
+    // on depth formats in ES2.
     GLuint fb = 0;
     glGenFramebuffersEXT(1, &fb);
     glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, fb);
 
     glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT,
                               target, texture->service_id(), level);
     bool have_stencil = (channels & GLES2Util::kStencil) != 0;
     if (have_stencil) {
       glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER_EXT, GL_STENCIL_ATTACHMENT,
                                 target, texture->service_id(), level);
@@ skipping 6648 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