super hacky opaque black clear bug workaround

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc

 // Copyright (c) 2016 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_passthrough.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "ui/gl/gl_version_info.h"
 
 namespace gpu {
@@ skipping 459 matching lines @@
     GLint drawbuffers,
     const volatile GLuint* value) {
   glClearBufferuiv(buffer, drawbuffers, const_cast<const GLuint*>(value));
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoClearColor(GLclampf red,
                                                        GLclampf green,
                                                        GLclampf blue,
                                                        GLclampf alpha) {
+  if (red == 0 && green == 0 && blue == 0 && alpha == 1) alpha = 1.001;
   glClearColor(red, green, blue, alpha);
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoClearDepthf(GLclampf depth) {
   glClearDepthf(depth);
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoClearStencil(GLint s) {
@@ skipping 3548 matching lines @@
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoSetEnableDCLayersCHROMIUM(
     GLboolean enable) {
   NOTIMPLEMENTED();
   return error::kNoError;
 }
 
 }  // namespace gles2
 }  // namespace gpu