WIP: Propagate SurfaceID up window tree hierarchy

cc/surfaces/frame_sink_id.h

Index: cc/surfaces/frame_sink_id.h
diff --git a/cc/surfaces/frame_sink_id.h b/cc/surfaces/frame_sink_id.h
new file mode 100644
index 0000000000000000000000000000000000000000..34295311cb0519db032bb141988ccf5c408d3b14
--- /dev/null
+++ b/cc/surfaces/frame_sink_id.h
@@ -0,0 +1,58 @@
+// Copyright 2016 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_SURFACES_FRAME_SINK_ID_H_
+#define CC_SURFACES_FRAME_SINK_ID_H_
+
+#include "base/format_macros.h"
+#include "base/hash.h"
+#include "base/strings/stringprintf.h"
+
+namespace cc {
+
+class FrameSinkId {
+ public:
+  FrameSinkId() : client_id_(0), sink_id_(0) {}
+
+  FrameSinkId(const FrameSinkId& other)
+      : client_id_(other.client_id_), sink_id_(other.sink_id_) {}
+
+  FrameSinkId(uint32_t client_id, uint32_t sink_id)
+      : client_id_(client_id), sink_id_(sink_id) {}
+
+  bool is_null() const { return client_id_ == 0 && sink_id_ == 0; }
+
+  size_t hash() const { return base::HashInts(client_id_, sink_id_); }
+
+  uint32_t client_id() const { return client_id_; }
+
+  uint32_t sink_id() const { return sink_id_; }
+
+  std::string ToString() const {
+    return base::StringPrintf("FrameSinkId(%d, %d)", client_id_, sink_id_);
+  }
+
+  bool operator==(const FrameSinkId& other) const {
+    return client_id_ == other.client_id_ && sink_id_ == other.sink_id_;
+  }
+
+  bool operator!=(const FrameSinkId& other) const { return !(*this == other); }
+
+  bool operator<(const FrameSinkId& other) const {
+    return std::tie(client_id_, sink_id_) <
+           std::tie(other.client_id_, other.sink_id_);
+  }
+
+ private:
+  uint32_t client_id_;
+  uint32_t sink_id_;
+};
+
+struct FrameSinkIdHash {
+  size_t operator()(const FrameSinkId& key) const { return key.hash(); }
+};
+
+}  // namespace cc
+
+#endif  // CC_SURFACES_FRAME_SINK_ID_H_