Add SwapPromise support to LayerTreeHost and LayerTreeImpl

cc/base/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_BASE_SWAP_PROMISE_H_
+#define CC_BASE_SWAP_PROMISE_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/callback_forward.h"
+
+namespace cc {
+
+struct SwapPromise {
+  SwapPromise(const base::Closure& did_swap_cb,
+              const base::Callback<void(const std::string&)>& swap_aborted_cb)
+      : did_swap_callback(did_swap_cb),
+        swap_aborted_callback(swap_aborted_cb) {}
+
+  ~SwapPromise() {}
+
+  base::Closure did_swap_callback;
+  base::Callback<void(const std::string&)> swap_aborted_callback;

[jamesr, 2013/11/12 03:15:04]

why does this take a std::string? from this patch it appears that only a small
set of strings could possibly be passed here, which would indicate that an enum
would be a better fit

[Yufeng Shen (Slow to review), 2013/11/13 21:05:04]

Done.

+};
+
+}  // namespace cc
+
+#endif  // CC_BASE_SWAP_PROMISE_H_