Command Buffer: read pixels into pixel pack buffer

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 "gpu/command_buffer/client/gles2_implementation.h"
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
@@ skipping 3523 matching lines @@
   uint32 unpadded_row_size;
   uint32 padded_row_size;
   if (!GLES2Util::ComputeImageDataSizes(
       width, 2, 1, format, type, pack_alignment_, &temp_size,
       &unpadded_row_size, &padded_row_size)) {
     SetGLError(GL_INVALID_VALUE, "glReadPixels", "size too large.");
     return;
   }
 
   if (bound_pixel_pack_buffer_) {
-    // TODO(zmo): Need to handle the case of reading into a PIXEL_PACK_BUFFER
-    // in ES3. For now, generate a GL error.
-    SetGLError(GL_INVALID_OPERATION, "glReadPixels",
-               "ReadPixels to a pixel pack buffer isn't implemented");
+    GLuint offset = ToGLuint(pixels);
+    helper_->ReadPixels(
+        xoffset, yoffset, width, height, format, type, 0, offset, 0, 0, false);
+    CheckGLError();
     return;
   }
 
   if (bound_pixel_pack_transfer_buffer_id_) {
     GLuint offset = ToGLuint(pixels);
     BufferTracker::Buffer* buffer = GetBoundPixelUnpackTransferBufferIfValid(
         bound_pixel_pack_transfer_buffer_id_,
         "glReadPixels", offset, padded_row_size * height);
     if (buffer && buffer->shm_id() != -1) {
       helper_->ReadPixels(xoffset, yoffset, width, height, format, type,
@@ skipping 2981 matching lines @@
   CheckGLError();
 }
 
 // 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/client/gles2_implementation_impl_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu