Plumb through EGL_NV_post_sub_buffer and GLX_MESA_copy_sub_buffer.

content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc

 // Copyright (c) 2011 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.
 
 #if defined(ENABLE_GPU)
 
 #include "content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h"
 
 #include "gpu/GLES2/gl2.h"
 #ifndef GL_GLEXT_PROTOTYPES
@@ skipping 274 matching lines @@
       &WebGraphicsContext3DCommandBufferImpl::OnSwapBuffersComplete,
       weak_ptr_factory_.GetWeakPtr()));
 #if defined(OS_MACOSX)
   // It appears that making the compositor's on-screen context current on
   // other platforms implies this flush. TODO(kbr): this means that the
   // TOUCH build and, in the future, other platforms might need this.
   gl_->Flush();
 #endif
 }
 
+void WebGraphicsContext3DCommandBufferImpl::postSubBufferCHROMIUM(
+    int x, int y, int width, int height) {
+  // Same flow control as WebGraphicsContext3DCommandBufferImpl::prepareTexture
+  // (see above).
+  RenderViewImpl* renderview =
+      web_view_ ? RenderViewImpl::FromWebView(web_view_) : NULL;
+  if (renderview)
+    renderview->OnViewContextSwapBuffersPosted();
+  gl_->PostSubBufferCHROMIUM(x, y, width, height);
+  context_->Echo(base::Bind(
+      &WebGraphicsContext3DCommandBufferImpl::OnSwapBuffersComplete,
+      weak_ptr_factory_.GetWeakPtr()));
+}
+
 void WebGraphicsContext3DCommandBufferImpl::reshape(int width, int height) {
   cached_width_ = width;
   cached_height_ = height;
 
   gl_->ResizeCHROMIUM(width, height);
 
 #ifdef FLIP_FRAMEBUFFER_VERTICALLY
   scanline_.reset(new uint8[width * 4]);
 #endif  // FLIP_FRAMEBUFFER_VERTICALLY
 }
@@ skipping 851 matching lines @@
   if (context_lost_callback_) {
     context_lost_callback_->onContextLost();
   }
   RenderViewImpl* renderview =
       web_view_ ? RenderViewImpl::FromWebView(web_view_) : NULL;
   if (renderview)
     renderview->OnViewContextSwapBuffersAborted();
 }
 
 #endif  // defined(ENABLE_GPU)