Reduce internal Flush() in GL resource glGen/Delete APIs.

gpu/command_buffer/client/cmd_buffer_helper.h

Index: gpu/command_buffer/client/cmd_buffer_helper.h
diff --git a/gpu/command_buffer/client/cmd_buffer_helper.h b/gpu/command_buffer/client/cmd_buffer_helper.h
index 513e00f69c880d3075e2a7e011f164a88195ba29..825cf9ffbe69702ad0f5394d16b6a9b8c45d9bf0 100644
--- a/gpu/command_buffer/client/cmd_buffer_helper.h
+++ b/gpu/command_buffer/client/cmd_buffer_helper.h
@@ -256,6 +256,8 @@ class GPU_EXPORT CommandBufferHelper {
     return ring_buffer_;
   }
 
+  uint32 flush_generation() const { return flush_generation_; }
+
   void FreeRingBuffer();
 
   bool HaveRingBuffer() const {
@@ -311,6 +313,10 @@ class GPU_EXPORT CommandBufferHelper {
   // Using C runtime instead of base because this file cannot depend on base.
   clock_t last_flush_time_;
 
+  // Incremented every time the helper flushes the command buffer.
+  // Can be used to track when prior commands have been flushed.
+  uint32 flush_generation_;
+
   friend class CommandBufferHelperTest;
   DISALLOW_COPY_AND_ASSIGN(CommandBufferHelper);
 };