Revert of Revert of Adding CopresenceState

components/copresence/public/copresence_state.h

Index: components/copresence/public/copresence_state.h
diff --git a/components/copresence/public/copresence_state.h b/components/copresence/public/copresence_state.h
new file mode 100644
index 0000000000000000000000000000000000000000..f922007815185b09a16ab1f34120c1bff6121385
--- /dev/null
+++ b/components/copresence/public/copresence_state.h
@@ -0,0 +1,47 @@
+// Copyright 2014 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 COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_STATE_H_
+#define COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_STATE_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+namespace copresence {
+
+class CopresenceObserver;
+class Directive;
+struct TransmittedToken;
+struct ReceivedToken;
+
+// This class tracks the state of the copresence component and can notify
+// interested parties when it changes. This is useful for debugging purposes.
+class CopresenceState {
+ public:
+  // Add a listener for future state changes. |observer| is owned by the caller,
+  // and must be valid until removed (or the CopresenceState is destroyed).
+  virtual void AddObserver(CopresenceObserver* observer) = 0;
+
+  // Remove a state change listener.
+  virtual void RemoveObserver(CopresenceObserver* observer) = 0;
+
+  // Accessor for the currently active directives.
+  virtual const std::vector<Directive>& active_directives() const = 0;
+
+  // Accessor for recently transmitted tokens.
+  virtual const std::map<std::string, TransmittedToken>&
+  transmitted_tokens() const = 0;
+
+  // Accessor for recently received tokens.
+  virtual const std::map<std::string, ReceivedToken>&
+  received_tokens() const = 0;
+
+ protected:
+  virtual ~CopresenceState() {}
+};
+
+}  // namespace copresence
+
+#endif  // COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_STATE_H_