Convert app_launch_index and page_index from int to StringOrdinal.

chrome/common/string_ordinal.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_COMMON_STRING_ORDINAL_H_
 #define CHROME_COMMON_STRING_ORDINAL_H_
 #pragma once
 
 #include <string>
 
@@ skipping 11 matching lines @@
 // has to change to represent the new order, and all the other older values
 // can stay the same.
 class StringOrdinal {
  public:
   // Creates a StringOrdinal from the given string. It may be valid or invalid.
   explicit StringOrdinal(const std::string& string_ordinal);
 
   // Creates an invalid StringOrdinal.
   StringOrdinal();
 
+  // Creates a valid StringOrdinal, this is generally called to create the first
+  // element of StringOrdinal list (i.e. before we have any other values we can
+  // generate from).
+  static StringOrdinal CreateValidOrdinal();
+
   bool IsValid() const;
 
   // All remaining functions can only be called if IsValid() holds.
   // It is an error to call them if IsValid() is false.
 
   // Order-related Functions
 
   // Returns true iff |*this| < |other|.
   bool LessThan(const StringOrdinal& other) const;
 
   // Returns true iff |*this| == |other| (i.e. |*this| < |other| and
   // |other| < |*this| are both false).
   bool Equal(const StringOrdinal& other) const;
 
   // Given |*this| != |other|, returns a StringOrdinal x such that
   // min(|*this|, |other|) < x < max(|*this|, |other|). It is an error
   // to call this function when |*this| == |other|.
   StringOrdinal CreateBetween(const StringOrdinal& other) const;
 
   // Returns a StringOrdinal |x| such that |x| < |*this|.
   StringOrdinal CreateBefore() const;
 
   // Returns a StringOrdinal |x| such that |*this| < |x|.
   StringOrdinal CreateAfter() const;
 
   // It is guaranteed that a StringOrdinal constructed from the returned
   // string will be valid.
   std::string ToString() const;
 
+  // A comparsion struct that can be use by STL containers that require sorting.
+  struct Comparsion {
+    bool operator() (const StringOrdinal& lhs, const StringOrdinal& rhs) const {
+      return lhs.LessThan(rhs);
+    }
+  };
+
   // Use of copy constructor and default assignment for this class is allowed.
 
  private:
   // The string representation of the StringOrdinal.
   std::string string_ordinal_;
 
   // The validity of the StringOrdinal (i.e., is it of the format [a-z]*[b-z]),
   // created to cache validity to prevent frequent recalculations.
   bool is_valid_;
 };
 
 #endif  // CHROME_COMMON_STRING_ORDINAL_H_