gpu: Defer reads from default framebuffer when needed.

gpu/command_buffer/client/gles2_implementation.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.
 
 // A class to emulate GLES2 over command buffers.
 
 #include "../client/gles2_implementation.h"
 
 #include <algorithm>
 #include <map>
@@ skipping 976 matching lines @@
   GPU_CLIENT_LOG("[" << GetLogPrefix() << "] glGetMaxValueInBufferCHROMIUM("
                  << buffer_id << ", " << count << ", "
                  << GLES2Util::GetStringGetMaxIndexType(type)
                  << ", " << offset << ")");
   GLuint result = GetMaxValueInBufferCHROMIUMHelper(
       buffer_id, count, type, offset);
   GPU_CLIENT_LOG("returned " << result);
   return result;
 }
 
-void GLES2Implementation::Clear(GLbitfield mask) {
-  GPU_CLIENT_SINGLE_THREAD_CHECK();
-  GPU_CLIENT_LOG("[" << GetLogPrefix() << "] glClear(" << mask << ")");
-  helper_->Clear(mask);
-}
-
 void GLES2Implementation::DrawElements(
     GLenum mode, GLsizei count, GLenum type, const void* indices) {
   GPU_CLIENT_SINGLE_THREAD_CHECK();
   GPU_CLIENT_LOG("[" << GetLogPrefix() << "] glDrawElements("
       << GLES2Util::GetStringDrawMode(mode) << ", "
       << count << ", "
       << GLES2Util::GetStringIndexType(type) << ", "
       << static_cast<const void*>(indices) << ")");
   if (count < 0) {
     SetGLError(GL_INVALID_VALUE, "glDrawElements", "count less than 0.");
@@ skipping 2646 matching lines @@
   return true;
 }
 
 // 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 "../client/gles2_implementation_impl_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu