Fix blue flashes on Mac

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 2464 matching lines @@
       LOG(ERROR) << "Offscreen saved FBO was incomplete.";
       Destroy(true);
       return false;
     }
 
     // Bind to the new default frame buffer (the offscreen target frame buffer).
     // This should now be associated with ID zero.
     DoBindFramebuffer(GL_FRAMEBUFFER, 0);
   }
 
-  // Clear the backbuffer.
-  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
-
   // OpenGL ES 2.0 implicitly enables the desktop GL capability
   // VERTEX_PROGRAM_POINT_SIZE and doesn't expose this enum. This fact
   // isn't well documented; it was discovered in the Khronos OpenGL ES
   // mailing list archives. It also implicitly enables the desktop GL
   // capability GL_POINT_SPRITE to provide access to the gl_PointCoord
   // variable in fragment shaders.
   if (gfx::GetGLImplementation() != gfx::kGLImplementationEGLGLES2) {
     glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
     glEnable(GL_POINT_SPRITE);
   }
@@ skipping 23 matching lines @@
   glActiveTexture(GL_TEXTURE0 + state_.active_texture_unit);
   glHint(GL_GENERATE_MIPMAP_HINT, state_.hint_generate_mipmap);
   glPixelStorei(GL_PACK_ALIGNMENT, state_.pack_alignment);
   glPixelStorei(GL_UNPACK_ALIGNMENT, state_.unpack_alignment);
 
   DoBindBuffer(GL_ARRAY_BUFFER, 0);
   DoBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
   DoBindFramebuffer(GL_FRAMEBUFFER, 0);
   DoBindRenderbuffer(GL_RENDERBUFFER, 0);
 
+  // Clear the backbuffer.
+  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
+
   if (feature_info_->workarounds().reverse_point_sprite_coord_origin) {
     glPointParameteri(GL_POINT_SPRITE_COORD_ORIGIN, GL_LOWER_LEFT);
   }
 
   if (feature_info_->workarounds().unbind_fbo_on_context_switch) {
     context_->SetUnbindFboOnMakeCurrent();
   }
 
   // Only compositor contexts are known to use only the subset of GL
   // that can be safely migrated between the iGPU and the dGPU. Mark
@@ skipping 7871 matching lines @@
   return error::kNoError;
 }
 
 // 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