Fix depth texture sampling on compatibility profile.

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 5221 matching lines @@
   if (texture_ref) {
     Texture* texture = texture_ref->texture();
     // Check that we are not trying to bind it to a different target.
     if (texture->target() != 0 && texture->target() != target) {
       LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION,
                          "glBindTexture",
                          "texture bound to more than 1 target.");
       return;
     }
     LogClientServiceForInfo(texture, client_id, "glBindTexture");
+    glBindTexture(target, texture->service_id());
     if (texture->target() == 0) {
       texture_manager()->SetTarget(texture_ref, target);
+      if (!feature_info_->gl_version_info().BehavesLikeGLES()) {
+        // We only need to do it for DEPTH textures on GL with compatibility
+        // profile, but this is simpler.
+        glTexParameteri(target, GL_DEPTH_TEXTURE_MODE, GL_RED);
+      }

[piman, 2016/05/18 21:00:15]

Can you explain to me why this is needed and what issue it solves? This is way
far from obvious.

     }
-    glBindTexture(target, texture->service_id());
   } else {
     glBindTexture(target, 0);
   }
 
   TextureUnit& unit = state_.texture_units[state_.active_texture_unit];
   unit.bind_target = target;
   unit.GetInfoForTarget(target) = texture_ref;
 }
 
 void GLES2DecoderImpl::DoBindSampler(GLuint unit, GLuint client_id) {
@@ skipping 11529 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