Clear old verified flush IDs when doing OrderingBarrier.

gpu/ipc/client/gpu_channel_host.h

Index: gpu/ipc/client/gpu_channel_host.h
diff --git a/gpu/ipc/client/gpu_channel_host.h b/gpu/ipc/client/gpu_channel_host.h
index 94fb98d71d6670bdf74bb0ce880a112b878d56db..247354b170911aa4c58976a2e8fc985fc556b84e 100644
--- a/gpu/ipc/client/gpu_channel_host.h
+++ b/gpu/ipc/client/gpu_channel_host.h
@@ -87,13 +87,15 @@ class GPU_EXPORT GpuChannelHost
   // Set an ordering barrier.  AsyncFlushes any pending barriers on other
   // routes. Combines multiple OrderingBarriers into a single AsyncFlush.
   // Returns the flush ID for the stream or 0 if put offset was not changed.
+  // Outputs *highest_verified_flush_id.
   uint32_t OrderingBarrier(int32_t route_id,
                            int32_t stream_id,
                            int32_t put_offset,
                            uint32_t flush_count,
                            const std::vector<ui::LatencyInfo>& latency_info,
                            bool put_offset_changed,
-                           bool do_flush);
+                           bool do_flush,
+                           uint32_t* highest_verified_flush_id);
 
   void FlushPendingStream(int32_t stream_id);