gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/common/gles2_cmd_format.h

Index: gpu/command_buffer/common/gles2_cmd_format.h
diff --git a/gpu/command_buffer/common/gles2_cmd_format.h b/gpu/command_buffer/common/gles2_cmd_format.h
index 252aafd06cf800695b969d1518bb344dcdacfe05..1c2534b18c27a1364bfa1798efd1678bb6f061a0 100644
--- a/gpu/command_buffer/common/gles2_cmd_format.h
+++ b/gpu/command_buffer/common/gles2_cmd_format.h
@@ -12,6 +12,7 @@
 
 #include <string.h>
 
+#include "base/atomicops.h"
 #include "gpu/command_buffer/common/bitfield_helpers.h"
 #include "gpu/command_buffer/common/cmd_buffer_common.h"
 #include "gpu/command_buffer/common/gles2_cmd_ids.h"
@@ -150,6 +151,25 @@ struct QuerySync {
   uint64 result;
 };
 
+struct AsyncUploadSync {
+  void Reset() {
+    base::subtle::Release_Store(&async_upload_token, 0);
+  }
+
+  void SetAsyncUploadToken(uint32 token) {
+    DCHECK_NE(token, 0u);
+    base::subtle::Release_Store(&async_upload_token, token);
+  }
+
+  bool HasAsyncUploadTokenPassed(uint32 token) {
+    DCHECK_NE(token, 0u);
+    uint32_t current_token = base::subtle::Acquire_Load(&async_upload_token);
+    return (current_token - token < 0x80000000);
+  }
+
+  base::subtle::Atomic32 async_upload_token;
+};
+
 COMPILE_ASSERT(sizeof(ProgramInput) == 20, ProgramInput_size_not_20);
 COMPILE_ASSERT(offsetof(ProgramInput, type) == 0,
                OffsetOf_ProgramInput_type_not_0);