Splitting DidSwap in cc::SwapPromise into WillSwap and DidSwap

cc/output/latency_info_swap_promise.h

 // Copyright 2013 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.
 
 #ifndef CC_OUTPUT_LATENCY_INFO_SWAP_PROMISE_H_
 #define CC_OUTPUT_LATENCY_INFO_SWAP_PROMISE_H_
 
 #include <stdint.h>
 
 #include "base/compiler_specific.h"
 #include "cc/output/swap_promise.h"
 #include "ui/events/latency_info.h"
 
 namespace cc {
 
 class CC_EXPORT LatencyInfoSwapPromise : public SwapPromise {
  public:
   explicit LatencyInfoSwapPromise(const ui::LatencyInfo& latency_info);
   ~LatencyInfoSwapPromise() override;
 
   void DidActivate() override {}
-  void DidSwap(CompositorFrameMetadata* metadata) override;
+  void WillSwap(CompositorFrameMetadata* metadata) override;
+  void DidSwap() override;
   DidNotSwapAction DidNotSwap(DidNotSwapReason reason) override;
   void OnCommit() override;
 
   int64_t TraceId() const override;
 
  private:
   ui::LatencyInfo latency_;
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_LATENCY_INFO_SWAP_PROMISE_H_