[WebGL 2] primitive restart should be always enabled

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 6136 matching lines @@
   if (error == GL_NO_ERROR) {
     framebuffer->AttachRenderbuffer(attachment, renderbuffer);
   }
   if (framebuffer == framebuffer_state_.bound_draw_framebuffer.get()) {
     framebuffer_state_.clear_state_dirty = true;
   }
   OnFboChanged();
 }
 
 void GLES2DecoderImpl::DoDisable(GLenum cap) {
+  if (cap == GL_PRIMITIVE_RESTART_FIXED_INDEX) {
+    // TODO(Yunchao): crbug.com/594021
+    // On Desktop GL with versions lower than 4.3, we need to emulate
+    // GL_PRIMITIVE_RESTART_FIXED_INDEX using glPrimitiveRestartIndex().
+    if (feature_info_->feature_flags().emulate_primitive_restart_fixed_index) {
+      return;

[Ken Russell (switch to Gerrit), 2016/03/19 00:06:41]

This short-circuit here and in DoEnable looks wrong to me. The
SetCapabilityState call is always needed -- that's how the command buffer tracks
whether the state is enabled or disabled. For the emulation on OpenGL <4.3, the
only thing that should be skipped is the glDisable/glEnable call.

+    }
+    buffer_manager()->SetPrimitiveRestartState(false);
+  }
   if (SetCapabilityState(cap, false)) {
     glDisable(cap);
   }
 }
 
 void GLES2DecoderImpl::DoEnable(GLenum cap) {
+  if (cap == GL_PRIMITIVE_RESTART_FIXED_INDEX) {
+    // TODO(Yunchao): crbug.com/594021
+    // On Desktop GL with versions lower than 4.3, we need to emulate
+    // GL_PRIMITIVE_RESTART_FIXED_INDEX using glPrimitiveRestartIndex().
+    if (feature_info_->feature_flags().emulate_primitive_restart_fixed_index) {
+      return;
+    }
+    buffer_manager()->SetPrimitiveRestartState(true);
+  }
   if (SetCapabilityState(cap, true)) {
     glEnable(cap);
   }
 }
 
 void GLES2DecoderImpl::DoDepthRangef(GLclampf znear, GLclampf zfar) {
   state_.z_near = std::min(1.0f, std::max(0.0f, znear));
   state_.z_far = std::min(1.0f, std::max(0.0f, zfar));
   glDepthRange(znear, zfar);
 }
@@ skipping 9955 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