Rename ModelType/ObjectIdStateMap to InvalidationMap.

sync/internal_api/public/base/invalidation.h

 // Copyright (c) 2012 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 SYNC_INTERNAL_API_PUBLIC_BASE_INVALIDATION_STATE_H_
-#define SYNC_INTERNAL_API_PUBLIC_BASE_INVALIDATION_STATE_H_
+#ifndef SYNC_INTERNAL_API_PUBLIC_BASE_INVALIDATION_H_
+#define SYNC_INTERNAL_API_PUBLIC_BASE_INVALIDATION_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 class DictionaryValue;
 class Value;
 }  // namespace
 
 namespace syncer {
 
 // Opaque class that represents an ack handle.
 // TODO(dcheng): This is just a refactoring change, so the class is empty for
 // the moment. It will be filled once we start implementing 'reminders'.
 class AckHandle {
  public:
   bool Equals(const AckHandle& other) const;
 
   scoped_ptr<base::Value> ToValue() const;
 
   bool ResetFromValue(const base::Value& value);
 };
 
-struct InvalidationState {
+// Represents a local invalidation, and is roughly analogous to
+// invalidation::Invalidation. It contains a payload (which may be empty) and an
+// associated ack handle that an InvalidationHandler implementation can use to
+// acknowledge receipt of the invalidation. It does not embed the object ID,
+// since it is typically associated with it through ObjectIdInvalidationMap.
+struct Invalidation {
   std::string payload;
   AckHandle ack_handle;
 
-  bool Equals(const InvalidationState& other) const;
+  bool Equals(const Invalidation& other) const;
 
   // Caller owns the returned DictionaryValue.
   scoped_ptr<base::DictionaryValue> ToValue() const;
 
   bool ResetFromValue(const base::DictionaryValue& value);
 };
 
 }  // namespace syncer
 
-#endif  // SYNC_INTERNAL_API_PUBLIC_BASE_INVALIDATION_STATE_H_
+#endif  // SYNC_INTERNAL_API_PUBLIC_BASE_INVALIDATION_H_