[Sync] Refactor sync datatype error handling.

chrome/browser/sync/api/sync_error.h

+// Copyright (c) 2011 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 CHROME_BROWSER_SYNC_API_SYNC_ERROR_H_
+#define CHROME_BROWSER_SYNC_API_SYNC_ERROR_H_
+#pragma once
+
+#include <string>
+
+#include "base/tracked.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/sync/syncable/model_type.h"
+
+// Sync errors are used for debug purposes and handled internally and/or
+// exposed through Chrome's "about:sync" internal page. They are considered
+// unrecoverable for the datatype creating them, and should only be used as
+// such.
+// This class is copy-friendly and thread-safe.
+class SyncError {
+ public:
+  // Default constructor refers to "no error", and is_set() will return false.
+  SyncError();
+
+  // Create a new Sync error triggered by datatype |type| with debug message
+  // |message| from the specified location.
+  SyncError(const tracked_objects::Location& location,
+            const std::string& message,
+            syncable::ModelType type);
+
+  // Copy-constructor.
+  SyncError(const SyncError& rhs);
+
+  // Reset the error to a new error.
+  // May be called irrespective of whether is_set() is true.
+  void Reset(const tracked_objects::Location& location,
+             const std::string& message,
+             syncable::ModelType type);
+
+  // Whether this is a valid error or not.
+  bool IsInitialized() const;
+
+  // These must only be called if is_set() is true.
+  const tracked_objects::Location& location() const;
+  const std::string& message() const;
+  const syncable::ModelType type() const;
+ private:
+  void print_log_error() const;
+
+  // Scoped_ptr is necessary because Location objects aren't assignable.
+  scoped_ptr<tracked_objects::Location> location_;
+  std::string message_;
+  syncable::ModelType type_;
+};
+
+#endif  // CHROME_BROWSER_SYNC_API_SYNC_ERROR_H_