Plumb through EGL_NV_post_sub_buffer and GLX_MESA_copy_sub_buffer.

webkit/gpu/webgraphicscontext3d_in_process_impl.cc

Index: webkit/gpu/webgraphicscontext3d_in_process_impl.cc
diff --git a/webkit/gpu/webgraphicscontext3d_in_process_impl.cc b/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
index 835bd61cc697b697e3b33efdd769785a79e8dcef..a1c8fefec7aebab418e99f370e0412fb395b28a5 100644
--- a/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
+++ b/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
@@ -333,6 +333,12 @@ void WebGraphicsContext3DInProcessImpl::prepareTexture() {
   }
 }
 
+void WebGraphicsContext3DInProcessImpl::postSubBufferCHROMIUM(
+    int x, int y, int width, int height) {
+  DCHECK(gl_surface_->SupportsPostSubBuffer());
+  gl_surface_->PostSubBuffer(x, y, width, height);
+}
+
 namespace {
 
 int CreateTextureObject(GLenum target) {