On desktop GL, don't disable vertex attribute 0 when restoring state, or nothing will be drawn duri…

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 <stdio.h>
 
 #include <algorithm>
 #include <list>
@@ skipping 5365 matching lines @@
   BufferManager::BufferInfo* buffer_info = info->buffer();
   glBindBuffer(GL_ARRAY_BUFFER, buffer_info ? buffer_info->service_id() : 0);
   glVertexAttribPointer(
       attrib, info->size(), info->type(), info->normalized(), info->gl_stride(),
       ptr);
   if (info->divisor())
     glVertexAttribDivisorANGLE(attrib, info->divisor());
   glBindBuffer(GL_ARRAY_BUFFER,
                bound_array_buffer_ ? bound_array_buffer_->service_id() : 0);
 
-  if (info->enabled()) {
-    glEnableVertexAttribArray(attrib);
-  } else {
-    glDisableVertexAttribArray(attrib);
+  // Never touch vertex attribute 0's state (in particular, never
+  // disable it) when running on desktop GL because it will never be
+  // re-enabled.
+  if (attrib != 0 ||
+      gfx::GetGLImplementation() == gfx::kGLImplementationEGLGLES2) {
+    if (info->enabled()) {
+      glEnableVertexAttribArray(attrib);
+    } else {
+      glDisableVertexAttribArray(attrib);
+    }
   }
 }
 
 bool GLES2DecoderImpl::SimulateFixedAttribs(
     const char* function_name,
     GLuint max_vertex_accessed, bool* simulated, GLsizei primcount) {
   DCHECK(simulated);
   *simulated = false;
   if (gfx::GetGLImplementation() == gfx::kGLImplementationEGLGLES2)
     return true;
@@ skipping 3786 matching lines @@
   BindAndApplyTextureParameters(info);
 }
 
 // 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 "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu