gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/service/query_manager.cc

Index: gpu/command_buffer/service/query_manager.cc
diff --git a/gpu/command_buffer/service/query_manager.cc b/gpu/command_buffer/service/query_manager.cc
index 85e273c6c3a02b570cc87b634823c577eaaf63a8..c8ccace5cab45dc08b8a41a78f4b02e6afd45c8d 100644
--- a/gpu/command_buffer/service/query_manager.cc
+++ b/gpu/command_buffer/service/query_manager.cc
@@ -12,6 +12,7 @@
 #include "base/time/time.h"
 #include "gpu/command_buffer/common/gles2_cmd_format.h"
 #include "gpu/command_buffer/service/async_pixel_transfer_manager.h"
+#include "gpu/command_buffer/service/cmd_buffer_engine.h"
 #include "gpu/command_buffer/service/error_state.h"
 #include "gpu/command_buffer/service/feature_info.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
@@ -24,8 +25,15 @@ namespace {
 class AsyncPixelTransferCompletionObserverImpl
     : public AsyncPixelTransferCompletionObserver {
  public:
-  AsyncPixelTransferCompletionObserverImpl(uint32 submit_count)
-      : submit_count_(submit_count),
+  AsyncPixelTransferCompletionObserverImpl(
+      base::WeakPtr<QueryManager> manager,
+      scoped_refptr<base::MessageLoopProxy> proxy,
+      uint32 submit_count,
+      uint32 serial)
+      : manager_(manager),
+        proxy_(proxy),
+        submit_count_(submit_count),
+        serial_(serial),
         cancelled_(false) {}
 
   void Cancel() {
@@ -46,13 +54,31 @@ class AsyncPixelTransferCompletionObserverImpl
       // submit_count was written to sync->process_count.
       base::subtle::MemoryBarrier();
       sync->process_count = submit_count_;
+
+      if (serial_) {
+        proxy_->PostTask(
+            FROM_HERE,
+            base::Bind(&AsyncPixelTransferCompletionObserverImpl::SetSerial,
+                       this));
+      }
     }
   }
 
  private:
   virtual ~AsyncPixelTransferCompletionObserverImpl() {}
 
+  void SetSerial() {
+    if (!manager_.get())
+      return;
+
+    manager_->decoder()->engine()->set_serial(serial_);
+  }
+
+  base::WeakPtr<QueryManager> manager_;
+  scoped_refptr<base::MessageLoopProxy> proxy_;
+
   uint32 submit_count_;
+  uint32 serial_;
 
   base::Lock lock_;
   bool cancelled_;
@@ -99,7 +125,10 @@ bool AsyncPixelTransfersCompletedQuery::End(uint32 submit_count) {
   mem_params.shm_data_offset = shm_offset();
   mem_params.shm_data_size = sizeof(QuerySync);
 
-  observer_ = new AsyncPixelTransferCompletionObserverImpl(submit_count);
+  scoped_refptr<base::MessageLoopProxy> proxy =
+      base::MessageLoop::current()->message_loop_proxy();
+  observer_ = new AsyncPixelTransferCompletionObserverImpl(
+      manager()->AsWeakPtr(), proxy, submit_count, serial());
 
   // Ask AsyncPixelTransferDelegate to run completion callback after all
   // previous async transfers are done. No guarantee that callback is run