Perform glReadPixels with PBOs in the gpu, if PBOs are available.

gpu/command_buffer/service/query_manager.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/query_manager.h"
 
 #include "base/atomicops.h"
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/shared_memory.h"
@@ skipping 177 matching lines @@
     DCHECK(mem_params.shared_memory->memory());
     void *data = static_cast<int8*>(mem_params.shared_memory->memory()) +
         mem_params.shm_data_offset;
     QuerySync* sync = static_cast<QuerySync*>(data);
 
     // Need a MemoryBarrier here to ensure that upload completed before
     // submit_count was written to sync->process_count.
     base::subtle::MemoryBarrier();
     sync->process_count = submit_count;
   }
+  void MarkAsCompletedStage1(
+      uint32 submit_count, const AsyncMemoryParams& mem_params);
 };
 
 AsyncPixelTransfersCompletedQuery::AsyncPixelTransfersCompletedQuery(
     QueryManager* manager, GLenum target, int32 shm_id, uint32 shm_offset)
     : Query(manager, target, shm_id, shm_offset) {
 }
 
 bool AsyncPixelTransfersCompletedQuery::Begin() {
   return true;
 }
 
 bool AsyncPixelTransfersCompletedQuery::End(uint32 submit_count) {
   AsyncMemoryParams mem_params;
   // Get the real shared memory since it might need to be duped to prevent
   // use-after-free of the memory.
   Buffer buffer = manager()->decoder()->GetSharedMemoryBuffer(shm_id());
   if (!buffer.shared_memory)
     return false;
   mem_params.shared_memory = buffer.shared_memory;
   mem_params.shm_size = buffer.size;
   mem_params.shm_data_offset = shm_offset();
   mem_params.shm_data_size = sizeof(QuerySync);
 
+  manager()->decoder()->WaitForReadPixels(
+      base::Bind(&AsyncPixelTransfersCompletedQuery::MarkAsCompletedStage1,
+                 this, submit_count, mem_params));
+  return AddToPendingTransferQueue(submit_count);
+}
+
+void AsyncPixelTransfersCompletedQuery::MarkAsCompletedStage1(
+    uint32 submit_count,
+    const AsyncMemoryParams& mem_params) {
+
   // Ask AsyncPixelTransferDelegate to run completion callback after all
   // previous async transfers are done. No guarantee that callback is run
   // on the current thread.
   manager()->decoder()->GetAsyncPixelTransferManager()->AsyncNotifyCompletion(
       mem_params,
       base::Bind(AsyncPixelTransfersCompletedQuery::MarkAsCompletedThreadSafe,
                  submit_count));
-
-  return AddToPendingTransferQueue(submit_count);
 }
 
 bool AsyncPixelTransfersCompletedQuery::Process() {
   QuerySync* sync = manager()->decoder()->GetSharedMemoryAs<QuerySync*>(
       shm_id(), shm_offset(), sizeof(*sync));
   if (!sync)
     return false;
 
   // Check if completion callback has been run. sync->process_count atomicity
   // is guaranteed as this is already used to notify client of a completed
@@ skipping 336 matching lines @@
 bool QueryManager::EndQuery(Query* query, uint32 submit_count) {
   DCHECK(query);
   if (!RemovePendingQuery(query)) {
     return false;
   }
   return query->End(submit_count);
 }
 
 }  // namespace gles2
 }  // namespace gpu